Access line disturbance mitigation

ABSTRACT

Methods, systems, and devices for access line disturbance mitigation are described to, for example, reduce voltage disturbances on deselected digit lines during a read or write operation. Memory cells of a memory device may be couplable with a write circuit including a level shifter circuit, such that changes in voltage on a selected digit line may be controlled via a level shifter circuit of a write circuit associated with a selected memory cell. The write circuit may write a logic state to the memory cell after completing a read operation. One or more write voltages may be applied to or removed from the memory cell via the level shifter circuit, which may control a slew rate of one or more voltage changes on the selected digit line. The slew rate(s) may be controlled via a current driver circuit coupled with a pull-up circuit or a pull-down circuit of the level shifter circuit.

CROSS REFERENCE

The present application for patent is a continuation of U.S. patentapplication Ser. No. 16/514,481 by Guo et al., entitled “FERROELECTRICMEMORY CELL WITH ACCESS LINE DISTURBANCE MITIGATION,” filed Jul. 17,2019, assigned to the assignee hereof, and is expressly incorporated byreference in its entirety herein.

BACKGROUND

The following relates generally to a system that includes at least onememory device and more specifically to access line disturbancemitigation.

Memory devices are widely used to store information in variouselectronic devices such as computers, wireless communication devices,cameras, digital displays, and the like. Information is stored byprogramming different states of a memory device. For example, binarydevices most often store one of two states, often denoted by a logic 1or a logic 0. In other devices, more than two states may be stored. Toaccess the stored information, a component of the device may read, orsense, at least one stored state in the memory device. To storeinformation, a component of the device may write, or program, the statein the memory device.

Various types of memory devices exist, including magnetic hard disks,random access memory (RAM), read-only memory (ROM), dynamic RAM (DRAM),synchronous dynamic RAM (SDRAM), ferroelectric RAM (FeRAM), magnetic RAM(MRAM), resistive RAM (RRAM), flash memory, phase change memory (PCM),and others. Memory devices may be volatile or non-volatile. Non-volatilememory, e.g., FeRAM, may maintain their stored logic state for extendedperiods of time even in the absence of an external power source.Volatile memory devices, e.g., DRAM, may lose their stored state whendisconnected from an external power source. FeRAM may be able to achievedensities similar to volatile memory but may have non-volatileproperties due to the use of a ferroelectric capacitor as a storagedevice.

In some memory devices, a change in voltage on a selected digit line ofa memory cell may cause voltage disturbances on one or more deselecteddigit lines (e.g., neighboring digit lines) via capacitive coupling.Disturbances in the voltage on deselected digit lines may impact a logicstate of memory cells coupled with the deselected digit lines (e.g., viaa cumulative hammering effect) that may occur over one or more voltagechanges.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a system that supports access linedisturbance mitigation in accordance with examples as disclosed herein.

FIG. 2 illustrates an example of a memory die that supports access linedisturbance mitigation in accordance with examples as disclosed herein.

FIGS. 3A and 3B illustrate examples of hysteresis curves that supportaccess line disturbance mitigation in accordance with examples asdisclosed herein.

FIG. 4 illustrates an example of a memory device that supports accessline disturbance mitigation in accordance with examples as disclosedherein.

FIGS. 5A and 5B illustrate examples of circuit diagrams that supportaccess line disturbance mitigation in accordance with examples asdisclosed herein.

FIGS. 6A and 6B illustrate examples of timing diagrams that supportaccess line disturbance mitigation in accordance with examples asdisclosed herein.

FIG. 7 shows a block diagram of a memory device that supports accessline disturbance mitigation in accordance with aspects of the presentdisclosure.

FIGS. 8 through 11 show flowcharts illustrating a method or methods thatsupport access line disturbance mitigation in accordance with examplesas disclosed herein.

DETAILED DESCRIPTION

A memory device may implement a memory cell selection procedure as partof a read or write operation, where the memory cell may be located at anintersection of a word line and a digit line. In some examples, thememory device may select the memory cell by applying a voltage to theword line and applying a voltage to the digit line (e.g., via aselection component). The voltage applied to the digit line may be usedto read, write, or perform other functions on the memory cell while thedigit line is coupled with the memory cell. In some examples, the memorydevice may deselect other digit lines between selected digit lines(e.g., by activating one or more components, such as shunts, to couplethe lines with a device plate). In some memory devices, a change involtage on the selected digit line may cause voltage disturbances on oneor more deselected digit lines (e.g., neighboring digit lines) viacapacitive coupling. Disturbances in the voltage on deselected digitlines may impact a logic state of memory cells coupled with thedeselected digit lines, for example, via a cumulative hammering effectthat may occur over multiple voltage changes.

To reduce (e.g., mitigate) voltage disturbances on the deselected digitlines, memory cells of memory device may be configured to be couplablewith a write circuit including a voltage level shifter circuit. Forexample, changes in voltage on a selected digit line may be controlledvia a voltage level shifter circuit of a write circuit associated with aselected memory cell. In some examples, the write circuit may be coupledwith a sense component (e.g., a latch) used to sense a logic state ofthe memory cell during a read operation. The write circuit may beconfigured to write a logic state to the memory cell (e.g., a same logicstate as previously stored on the memory cell or a different logicstate) after completing the read operation. A first voltage (e.g., awrite voltage) may be applied to the memory cell via a level shiftercircuit (e.g., a dynamic level shifter circuit), and the level shiftercircuit may control a slew rate of the first voltage change along theselected digit line (e.g., to bring the selected digit line to the writevoltage). For example, the slew rate of the write voltage may becontrolled via a current mirror circuit (e.g., current driver circuit orcurrent follower circuit) coupled with a pull-up circuit of the dynamiclevel shifter circuit. The current mirror circuit may control a voltageor a current applied to the pull-up circuit. In some examples, loweringor otherwise adjusting the slew rate of the first voltage change alongthe selected digit line may result in lower voltage disturbances alongneighboring digit lines.

In some examples, the selected digit line may also be grounded throughthe dynamic level shifter circuit. In some examples, grounding theselected digit line may apply a write voltage to the selected digit line(e.g., if a write voltage is a grounded voltage). In some examples,grounding the selected digit line may remove a write voltage (e.g., thefirst voltage) from the selected digit line, which may result in asecond voltage change along the selected digit line. The slew rate ofthe second voltage change may be controlled via a current driver circuitcoupled with a pull-down circuit of the dynamic level shifter circuit(e.g., by controlling a voltage applied to the pull-down circuit).Controlling the slew rate of the second voltage change may result inlower voltage disturbances along neighboring digit lines, as describedabove. As such, memory cells coupled with the neighboring digit linesmay be unaffected or may not change a logic state as a result of thelower voltage disturbances.

Features of the disclosure are initially described in the context of amemory system and memory die as described with reference to FIGS. 1-3.Features of the disclosure are described in the context of a memorydevice, circuit diagrams, and timing diagrams as illustrated in FIGS.4-6. These and other features of the disclosure are further illustratedby and described with reference to an apparatus diagram and flowchartsthat relate to access line disturbance mitigation as described withreference to FIGS. 7-11.

FIG. 1 illustrates an example of a system 100 that utilizes one or morememory devices in accordance with examples as disclosed herein. Thesystem 100 may include an external memory controller 105, a memorydevice 110, and a plurality of channels 115 coupling the external memorycontroller 105 with the memory device 110. The system 100 may includeone or more memory devices, but for ease of description the one or morememory devices may be described as a single memory device 110.

The system 100 may include portions of an electronic device, such as acomputing device, a mobile computing device, a wireless device, or agraphics processing device. The system 100 may be an example of aportable electronic device. The system 100 may be an example of acomputer, a laptop computer, a tablet computer, a smartphone, a cellularphone, a wearable device, an internet-connected device, or the like. Thememory device 110 may be component of the system configured to storedata for one or more other components of the system 100. In someexamples, the system 100 is capable of machine-type communication (MTC),machine-to-machine (M2M) communication, or device-to-device (D2D)communication.

At least portions of the system 100 may be examples of a host device.Such a host device may be an example of a device that uses memory toexecute processes such as a computing device, a mobile computing device,a wireless device, a graphics processing device, a computer, a laptopcomputer, a tablet computer, a smartphone, a cellular phone, a wearabledevice, an internet-connected device, some other stationary or portableelectronic device, or the like. In some examples, the host device mayrefer to the hardware, firmware, software, or a combination thereof thatimplements the functions of the external memory controller 105. In someexamples, the external memory controller 105 may be referred to as ahost or host device. In some examples, system 100 is a graphics card.

In some examples, a memory device 110 may be an independent device orcomponent that is configured to be in communication with othercomponents of the system 100 and provide physical memory addresses/spaceto potentially be used or referenced by the system 100. In someexamples, a memory device 110 may be configurable to work with at leastone or a plurality of different types of systems 100. Signaling betweenthe components of the system 100 and the memory device 110 may beoperable to support modulation schemes to modulate the signals,different pin designs for communicating the signals, distinct packagingof the system 100 and the memory device 110, clock signaling andsynchronization between the system 100 and the memory device 110, timingconventions, and/or other factors.

The memory device 110 may be configured to store data for the componentsof the system 100. In some examples, the memory device 110 may act as aslave-type device to the system 100 (e.g., responding to and executingcommands provided by the system 100 through the external memorycontroller 105). Such commands may include an access command for anaccess operation, such as a write command for a write operation, a readcommand for a read operation, a refresh command for a refresh operation,or other commands. The memory device 110 may include two or more memorydice 160 (e.g., memory chips) to support a desired or specified capacityfor data storage. The memory device 110 including two or more memorydice may be referred to as a multi-die memory or package (also referredto as multi-chip memory or package).

The system 100 may further include a processor 120, a basic input/outputsystem (BIOS) component 125, one or more peripheral components 130, andan input/output (I/O) controller 135. The components of system 100 maybe in electronic communication with one another using a bus 140.

The processor 120 may be configured to control at least portions of thesystem 100. The processor 120 may be a general-purpose processor, adigital signal processor (DSP), an application-specific integratedcircuit (ASIC), a field-programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or it may be a combination of these types ofcomponents. In such examples, the processor 120 may be an example of acentral processing unit (CPU), a graphics processing unit (GPU), ageneral purpose graphic processing unit (GPGPU), or a system on a chip(SoC), among other examples.

The BIOS component 125 may be a software component that includes a BIOSoperated as firmware, which may initialize and run various hardwarecomponents of the system 100. The BIOS component 125 may also managedata flow between the processor 120 and the various components of thesystem 100, e.g., the peripheral components 130, the I/O controller 135,etc. The BIOS component 125 may include a program or software stored inread-only memory (ROM), flash memory, or any other non-volatile memory.

The peripheral component(s) 130 may be any input device or outputdevice, or an interface for such devices, that may be integrated into orwith the system 100. Examples may include disk controllers, soundcontroller, graphics controller, Ethernet controller, modem, universalserial bus (USB) controller, a serial or parallel port, or peripheralcard slots, such as peripheral component interconnect (PCI) orspecialized graphics ports. The peripheral component(s) 130 may be othercomponents understood by those skilled in the art as peripherals.

The I/O controller 135 may manage data communication between theprocessor 120 and the peripheral component(s) 130, input devices 145, oroutput devices 150. The I/O controller 135 may manage peripherals thatare not integrated into or with the system 100. In some examples, theI/O controller 135 may represent a physical connection or port toexternal peripheral components.

The input 145 may represent a device or signal external to the system100 that provides information, signals, or data to the system 100 or itscomponents. This may include a user interface or interface with orbetween other devices. In some examples, the input 145 may be aperipheral that interfaces with system 100 via one or more peripheralcomponents 130 or may be managed by the I/O controller 135.

The output 150 may represent a device or signal external to the system100 configured to receive an output from the system 100 or any of itscomponents. Examples of the output 150 may include a display, audiospeakers, a printing device, or another processor on printed circuitboard, and so forth. In some examples, the output 150 may be aperipheral that interfaces with the system 100 via one or moreperipheral components 130 or may be managed by the I/O controller 135.

The components of system 100 may be made up of general-purpose orspecial purpose circuitry designed to carry out their functions. Thismay include various circuit elements, for example, conductive lines,transistors, capacitors, inductors, resistors, amplifiers, or otheractive or passive elements, configured to carry out the functionsdescribed herein.

The memory device 110 may include a device memory controller 155 and oneor more memory dice 160. Each memory die 160 may include a local memorycontroller 165 (e.g., local memory controller 165-a, local memorycontroller 165-b, and/or local memory controller 165-N) and a memoryarray 170 (e.g., memory array 170-a, memory array 170-b, and/or memoryarray 170-N). A memory array 170 may be a collection (e.g., a grid) ofmemory cells, with each memory cell being configured to store at leastone bit of digital data. Features of memory arrays 170 and/or memorycells are described in more detail with reference to FIG. 2. A memoryarray 170 may be configured such that memory cells are couplable with awrite circuit, which may include a level shifter circuit, as describedwith reference to FIGS. 4-5B.

The memory device 110 may be an example of a two-dimensional (2D) arrayof memory cells or may be an example of a three-dimensional (3D) arrayof memory cells. For example, a 2D memory device may include a singlememory die 160. A 3D memory device may include two or more memory dice160 (e.g., memory die 160-a, memory die 160-b, and/or any quantity ofmemory dice 160-N). In a 3D memory device, a plurality of memory dice160-N may be stacked on top of one another or next to one another. Insome examples, memory dice 160-N in a 3D memory device may be referredto as decks, levels, layers, or dies. A 3D memory device may include anyquantity of stacked memory dice 160-N (e.g., two high, three high, fourhigh, five high, six high, seven high, eight high). This may increasethe quantity of memory cells that may be positioned on a substrate ascompared with a single 2D memory device, which in turn may reduceproduction costs or increase the performance of the memory array, orboth. In some 3D memory device, different decks may share at least onecommon access line such that some decks may share at least one of a wordline, a digit line, and/or a plate line.

The device memory controller 155 may include circuits or componentsconfigured to control operation of the memory device 110. As such, thedevice memory controller 155 may include the hardware, firmware, andsoftware that enables the memory device 110 to perform commands and maybe configured to receive, transmit, or execute commands, data, orcontrol information related to the memory device 110. The device memorycontroller 155 may be configured to communicate with the external memorycontroller 105, the one or more memory dice 160, or the processor 120.In some examples, the memory device 110 may receive data and/or commandsfrom the external memory controller 105. For example, the memory device110 may receive a write command indicating that the memory device 110 isto store certain data on behalf of a component of the system 100 (e.g.,the processor 120) or a read command indicating that the memory device110 is to provide certain data stored in a memory die 160 to a componentof the system 100 (e.g., the processor 120). In some examples, thedevice memory controller 155 may control operation of the memory device110 described herein in conjunction with the local memory controller 165of the memory die 160. Examples of the components included in the devicememory controller 155 and/or the local memory controllers 165 mayinclude receivers for demodulating signals received from the externalmemory controller 105, decoders for modulating and transmitting signalsto the external memory controller 105, logic, decoders, amplifiers,filters, or the like.

The local memory controller 165 (e.g., local to a memory die 160) may beconfigured to control operations of the memory die 160. Also, the localmemory controller 165 may be configured to communicate (e.g., receiveand transmit data and/or commands) with the device memory controller155. The local memory controller 165 may support the device memorycontroller 155 to control operation of the memory device 110 asdescribed herein. In some examples, the memory device 110 does notinclude the device memory controller 155, and the local memorycontroller 165 or the external memory controller 105 may perform thevarious functions described herein. As such, the local memory controller165 may be configured to communicate with the device memory controller155, with other local memory controllers 165, or directly with theexternal memory controller 105 or the processor 120.

The external memory controller 105 may be configured to enablecommunication of information, data, and/or commands between componentsof the system 100 (e.g., the processor 120) and the memory device 110.The external memory controller 105 may act as a liaison between thecomponents of the system 100 and the memory device 110 so that thecomponents of the system 100 may not need to know the details of thememory device's operation. The components of the system 100 may presentrequests to the external memory controller 105 (e.g., read commands orwrite commands) that the external memory controller 105 satisfies. Theexternal memory controller 105 may convert or translate communicationsexchanged between the components of the system 100 and the memory device110. In some examples, the external memory controller 105 may include asystem clock that generates a common (source) system clock signal. Insome examples, the external memory controller 105 may include a commondata clock that generates a common (source) data clock signal.

In some examples, the external memory controller 105 or other componentof the system 100, or its functions described herein, may be implementedby the processor 120. For example, the external memory controller 105may be hardware, firmware, or software, or some combination thereofimplemented by the processor 120 or other component of the system 100.While the external memory controller 105 is depicted as being externalto the memory device 110, in some examples, the external memorycontroller 105, or its functions described herein, may be implemented bya memory device 110. For example, the external memory controller 105 maybe hardware, firmware, or software, or some combination thereofimplemented by the device memory controller 155 or one or more localmemory controllers 165. In some examples, the external memory controller105 may be distributed across the processor 120 and the memory device110 such that portions of the external memory controller 105 areimplemented by the processor 120 and other portions are implemented by adevice memory controller 155 or a local memory controller 165. Likewise,in some examples, one or more functions ascribed herein to the devicememory controller 155 or local memory controller 165 may in someexamples be performed by the external memory controller 105 (eitherseparate from or as included in the processor 120).

The components of the system 100 may exchange information with thememory device 110 using a plurality of channels 115. In some examples,the channels 115 may enable communications between the external memorycontroller 105 and the memory device 110. Each channel 115 may includeone or more signal paths or transmission mediums (e.g., conductors)between terminals associated with the components of system 100. Forexample, a channel 115 may include a first terminal including one ormore pins or pads at external memory controller 105 and one or more pinsor pads at the memory device 110. A pin may be an example of aconductive input or output point of a device of the system 100, and apin may be configured to act as part of a channel. In some examples, apin or pad of a terminal may be part of to a signal path of the channel115. Additional signal paths may be coupled with a terminal of a channelfor routing signals within a component of the system 100. For example,the memory device 110 may include signal paths (e.g., signal pathsinternal to the memory device 110 or its components, such as internal toa memory die 160) that route a signal from a terminal of a channel 115to the various components of the memory device 110 (e.g., a devicememory controller 155, memory dice 160, local memory controllers 165,memory arrays 170).

Channels 115 (and associated signal paths and terminals) may bededicated to communicating specific types of information. In someexamples, a channel 115 may be an aggregated channel and thus mayinclude multiple individual channels. For example, a data channel 190may be ×4 (e.g., including four signal paths), ×8 (e.g., including eightsignal paths), ×16 (e.g., including sixteen signal paths), and so forth.Signals communicated over the channels may use a double data rate (DDR)timing scheme. For example, some symbols of a signal may be registeredon a rising edge of a clock signal and other symbols of the signal maybe registered on a falling edge of the clock signal. Signalscommunicated over channels may use single data rate (SDR) signaling. Forexample, one symbol of the signal may be registered for each clockcycle.

In some examples, the channels 115 may include one or more command andaddress (CA) channels 186. The CA channels 186 may be configured tocommunicate commands between the external memory controller 105 and thememory device 110 including control information associated with thecommands (e.g., address information). For example, the CA channel 186may include a read command with an address of the desired data. In someexamples, the CA channels 186 may be registered on a rising clock signaledge and/or a falling clock signal edge. In some examples, a CA channel186 may include any quantity of signal paths to decode address andcommand data (e.g., eight or nine signal paths).

In some examples, the channels 115 may include one or more clock signal(CK) channels 188. The CK channels 188 may be configured to communicateone or more common clock signals between the external memory controller105 and the memory device 110. Each clock signal may be configured tooscillate between a high state and a low state and coordinate theactions of the external memory controller 105 and the memory device 110.In some examples, the clock signal may be a differential output (e.g., aCK_t signal and a CK_c signal) and the signal paths of the CK channels188 may be configured accordingly. In some examples, the clock signalmay be single ended. A CK channel 188 may include any quantity of signalpaths. In some examples, the clock signal CK (e.g., a CK_t signal and aCK_c signal) may provide a timing reference for command and addressingoperations for the memory device 110, or other system-wide operationsfor the memory device 110. The clock signal CK may therefore bevariously referred to as a control clock signal CK, a command clocksignal CK, or a system clock signal CK. The system clock signal CK maybe generated by a system clock, which may include one or more hardwarecomponents (e.g., oscillators, crystals, logic gates, transistors, orthe like).

In some examples, the channels 115 may include one or more data (DQ)channels 190. The data channels 190 may be configured to communicatedata and/or control information between the external memory controller105 and the memory device 110. For example, the data channels 190 maycommunicate information (e.g., bi-directional) to be written to thememory device 110 or information read from the memory device 110.

In some examples, the channels 115 may include one or more otherchannels 192 that may be dedicated to other purposes. These otherchannels 192 may include any quantity of signal paths.

In some examples, the other channels 192 may include one or more writeclock signal (WCK) channels. While the ‘W’ in WCK may nominally standfor “write,” a write clock signal WCK (e.g., a WCK_t signal and a WCK_csignal) may provide a timing reference for access operations generallyfor the memory device 110 (e.g., a timing reference for both read andwrite operations). Accordingly, the write clock signal WCK may also bereferred to as a data clock signal WCK. The WCK channels may beconfigured to communicate a common data clock signal between theexternal memory controller 105 and the memory device 110. The data clocksignal may be configured to coordinate an access operation (e.g., awrite operation or read operation) of the external memory controller 105and the memory device 110. In some examples, the write clock signal maybe a differential output (e.g., a WCK_t signal and a WCK_c signal) andthe signal paths of the WCK channels may be configured accordingly. AWCK channel may include any quantity of signal paths. The data clocksignal WCK may be generated by a data clock, which may include one ormore hardware components (e.g., oscillators, crystals, logic gates,transistors, or the like).

In some examples, the other channels 192 may include one or more errordetection code (EDC) channels. The EDC channels may be configured tocommunicate error detection signals, such as checksums, to improvesystem reliability. An EDC channel may include any quantity of signalpaths.

The channels 115 may couple the external memory controller 105 with thememory device 110 using a variety of different architectures. Examplesof the various architectures may include a bus, a point-to-pointconnection, a crossbar, a high-density interposer such as a siliconinterposer, or channels formed in an organic substrate or somecombination thereof. For example, in some examples, the signal paths mayat least partially include a high-density interposer, such as a siliconinterposer or a glass interposer.

Signals communicated over the channels 115 may be modulated using avariety of different modulation schemes. In some examples, abinary-symbol (or binary-level) modulation scheme may be used tomodulate signals communicated between the external memory controller 105and the memory device 110. A binary-symbol modulation scheme may be anexample of a M-ary modulation scheme where M is equal to two. Eachsymbol of a binary-symbol modulation scheme may be configured torepresent one bit of digital data (e.g., a symbol may represent a logic1 or a logic 0). Examples of binary-symbol modulation schemes include,but are not limited to, non-return-to-zero (NRZ), unipolar encoding,bipolar encoding, Manchester encoding, pulse amplitude modulation (PAM)having two symbols (e.g., PAM2), and/or others.

In some examples, a multi-symbol (or multi-level) modulation scheme maybe used to modulate signals communicated between the external memorycontroller 105 and the memory device 110. A multi-symbol modulationscheme may be an example of a M-ary modulation scheme where M is greaterthan or equal to three. Each symbol of a multi-symbol modulation schememay be configured to represent more than one bit of digital data (e.g.,a symbol may represent a logic 00, a logic 01, a logic 10, or a logic11). Examples of multi-symbol modulation schemes include, but are notlimited to, PAM3, PAM4, PAM8, etc., quadrature amplitude modulation(QAM), quadrature phase shift keying (QPSK), and/or others. Amulti-symbol signal (e.g., PAM3 signal or PAM4 signal) may be a signalthat is modulated using a modulation scheme that includes at least threelevels to encode more than one bit of information per symbol.Multi-symbol modulation schemes and symbols may alternatively bereferred to as non-binary, multi-bit, or higher-order modulation schemesand symbols.

To reduce (e.g., mitigate) voltage disturbances on deselected digitlines, memory cells of memory device 110 may be configured to becouplable with a write circuit including a voltage level shiftercircuit. A first voltage (e.g., a write voltage) may be applied to amemory cell via a level shifter circuit, and the level shifter circuitmay control a slew rate of a first voltage change along an associateddigit line. In some examples, the digit line may also be groundedthrough the level shifter circuit, which in some examples, which mayresult in a second voltage change along the selected digit line, where aslew rate of the second voltage change may be controlled by the levelshifter circuit. In some examples, lowering or otherwise adjusting theslew rate of the voltage changes along the digit line may result inlower voltage disturbances along neighboring digit lines. As such,memory cells coupled with neighboring, deselected digit lines may beunaffected or may not change a logic state as a result of the lowervoltage disturbances.

FIG. 2 illustrates an example of a memory die 200 in accordance withexamples as disclosed herein. The memory die 200 may be an example ofthe memory dice 160 described with reference to FIG. 1. In someexamples, the memory die 200 may be referred to as a memory chip, amemory device, or an electronic memory apparatus. The memory die 200 mayinclude one or more memory cells 205 that are programmable to storedifferent logic states. Each memory cell 205 may be programmable tostore two or more states. For example, the memory cell 205 may beconfigured to store one bit of information at a time (e.g., a logic 0 ora logic 1). In some examples, a single memory cell 205 (e.g., amulti-level memory cell) may be configured to store more than one bit ofinformation at a time (e.g., a logic 00, logic 01, logic 10, or a logic11).

A memory cell 205 may store a state (e.g., polarization state ordielectric charge) that represents digital data. In FeRAM architectures,the memory cell 205 may include a capacitor that includes aferroelectric material to store a charge and/or a polarizationrepresentative of the programmable state. In DRAM architectures, thememory cell 205 may include a capacitor that includes a dielectricmaterial to store a charge representative of the programmable state.

Operations such as reading and writing may be performed on memory cells205 by activating or selecting access lines such as a word line 210, adigit line 215, and/or a plate line 220. In some examples, digit lines215 may also be referred to as bit lines. References to access lines,word lines, digit lines, plate lines or their analogues, areinterchangeable without loss of understanding or operation. Activatingor selecting a word line 210, a digit line 215, or a plate line 220 mayinclude applying a voltage to the respective line.

The memory die 200 may include the access lines (e.g., the word lines210, the digit lines 215, and the plate lines 220) arranged in agrid-like pattern. Memory cells 205 may be positioned at intersectionsof the word lines 210, the digit lines 215, and/or the plate lines 220.By biasing a word line 210, a digit line 215, and a plate line 220(e.g., applying a voltage to the word line 210, digit line 215, or plateline 220), a single memory cell 205 may be accessed at theirintersection.

Accessing the memory cells 205 may be controlled through a row decoder225, a column decoder 230, and a plate driver 235. For example, a rowdecoder 225 may receive a row address from the local memory controller265 and activate a word line 210 based on the received row address. Acolumn decoder 230 receives a column address from the local memorycontroller 265 and activates a digit line 215 based on the receivedcolumn address. A plate driver 235 may receive a plate address from thelocal memory controller 265 and activates a plate line 220 based on thereceived plate address. For example, the memory die 200 may includemultiple word lines 210, labeled WL_1 through WL_M, multiple digit lines215, labeled DL_1 through DL_N, and multiple plate lines, labeled PL_1through PL_P, where M, N, and P depend on the size of the memory array.Thus, by activating a word line 210, a digit line 215, and a plate line220, e.g., WL_1, DL_3, and PL_1, the memory cell 205 at theirintersection may be accessed. The intersection of a word line 210 and adigit line 215, in either a two-dimensional or three-dimensionalconfiguration, may be referred to as an address of a memory cell 205. Insome examples, the intersection of a word line 210, a digit line 215,and a plate line 220 may be referred to as an address of the memory cell205.

The memory cell 205 may include a logic storage component, such ascapacitor 240, and a switching component 245. The capacitor 240 may bean example of a ferroelectric capacitor. A first node of the capacitor240 may be coupled with the switching component 245 and a second node ofthe capacitor 240 may be coupled with a plate line 220. The switchingcomponent 245 may be an example of a transistor or any other type ofswitch device that selectively establishes or de-establishes electroniccommunication between two components.

Selecting or deselecting the memory cell 205 may be accomplished byactivating or deactivating the switching component 245. The capacitor240 may be in electronic communication with the digit line 215 using theswitching component 245. For example, the capacitor 240 may be isolatedfrom digit line 215 when the switching component 245 is deactivated, andthe capacitor 240 may be coupled with digit line 215 when the switchingcomponent 245 is activated. In some examples, the switching component245 is a transistor and its operation is controlled by applying avoltage to a transistor gate, where the voltage differential between thetransistor gate and transistor source is greater or less than athreshold voltage of the transistor. In some examples, the switchingcomponent 245 may be a p-type transistor or an n-type transistor. Theword line 210 may be in electronic communication with the gate of theswitching component 245 and may activate/deactivate the switchingcomponent 245 based on a voltage being applied to word line 210.

A word line 210 may be a conductive line in electronic communicationwith a memory cell 205 that is used to perform access operations on thememory cell 205. In some architectures, the word line 210 may be inelectronic communication with a gate of a switching component 245 of amemory cell 205 and may be configured to control the switching component245 of the memory cell. In some architectures, the word line 210 may bein electronic communication with a node of the capacitor of the memorycell 205 and the memory cell 205 may not include a switching component.

A digit line 215 may be a conductive line that connects the memory cell205 with a sense component 250. In some architectures, the memory cell205 may be selectively coupled with the digit line 215 during portionsof an access operation. For example, the word line 210 and the switchingcomponent 245 of the memory cell 205 may be configured to selectivelycouple and/or isolate the capacitor 240 of the memory cell 205 and thedigit line 215. In some architectures, the memory cell 205 may be inelectronic communication (e.g., constant) with the digit line 215. Thedigit line 215 may be coupled with a write circuit that may include alevel shifter circuit, where the level shifter circuit may controlvoltages applied to the digit line 215 and/or removed from the digitline 215 during write operations.

A plate line 220 may be a conductive line in electronic communicationwith a memory cell 205 that is used to perform access operations on thememory cell 205. The plate line 220 may be in electronic communicationwith a node (e.g., the cell bottom) of the capacitor 240. The plate line220 may be configured to cooperate with the digit line 215 to bias thecapacitor 240 during access operation of the memory cell 205.

The sense component 250 may be configured to determine a state (e.g., apolarization state or a charge) stored on the capacitor 240 of thememory cell 205 and determine a logic state of the memory cell 205 basedon the detected state. The charge stored by a memory cell 205 may beextremely small, in some examples. As such, the sense component 250 mayinclude one or more sense amplifiers to amplify the signal output of thememory cell 205. The sense amplifiers may detect minute changes in thecharge of a digit line 215 during a read operation and may producesignals corresponding to either a logic 0 or a logic 1 based on thedetected charge. During a read operation, the capacitor 240 of memorycell 205 may output a signal (e.g., discharge a charge) to itscorresponding digit line 215. The signal may cause a voltage of thedigit line 215 to change. The sense component 250 may be configured tocompare the signal received from the memory cell 205 across the digitline 215 to a reference signal 255 (e.g., a reference voltage). In somecases, the sense component 250 may integrate charge read from a memorycell 205 via a digit line 215 after a word line 210 is activated and mayoutput an integrated charge level. The sense component 250 may determinethe stored state of the memory cell 205 based on the comparison. Forexample, in binary-signaling, if digit line 215 has a higher voltagethan the reference signal 255, the sense component 250 may determinethat the stored state of memory cell 205 is a logic 1, and, if the digitline 215 has a lower voltage than the reference signal 255, the sensecomponent 250 may determine that the stored state of the memory cell 205is a logic 0. The sense component 250 may include various transistors oramplifiers to detect and amplify a difference in the signals. Thedetected logic state of the memory cell 205 may be provided as an outputof the sense component 250 (e.g., to an input/output 260), and mayindicate the detected logic state to another component of a memorydevice 110 that includes the memory die 200, such as a device memorycontroller 155 (e.g., directly or using the local memory controller265). In some examples, the sense component 250 may be in electroniccommunication with the row decoder 225, the column decoder 230, and/orthe plate driver 235. The sense component 250 may be selectivelycouplable with one or more digit lines 215, and may be coupled with adigit line 215 to read and/or write data associated with a memory cellof the digit line 215. The sense component 250 may also be selectivelycouplable with the write circuit described above, and may provide alogic state to the write circuit to be written back to a memory cell 205via the level shifter circuit. In some examples, the sense component 250may include transistors with a thin gate oxide thickness and may operateusing a lower voltage than other components.

The local memory controller 265 may control the operation of memorycells 205 through the various components (e.g., row decoder 225, columndecoder 230, plate driver 235, and sense component 250). The localmemory controller 265 may be an example of the local memory controller165 described with reference to FIG. 1. In some examples, one or more ofthe row decoder 225, column decoder 230, and plate driver 235, and sensecomponent 250 may be co-located with the local memory controller 265.The local memory controller 265 may be configured to receive one or morecommands and/or data from an external memory controller 105 (or a devicememory controller 155 described with reference to FIG. 1), translate thecommands and/or data into information that can be used by the memory die200, perform one or more operations on the memory die 200, andcommunicate data from the memory die 200 to the external memorycontroller 105 (or the device memory controller 155) in response toperforming the one or more operations. The local memory controller 265may generate row, column, and/or plate line address signals to activatethe target word line 210, the target digit line 215, and the targetplate line 220. The local memory controller 265 may also generate andcontrol various voltages or currents used during the operation of thememory die 200. In general, the amplitude, shape, or duration of anapplied voltage or current discussed herein may be adjusted or variedand may be different for the various operations discussed in operatingthe memory die 200. A memory controller 265 may control a slew rate ofone or more voltage changes along a selected digit line 215, accordingto the methods and devices described herein.

In some examples, the local memory controller 265 may be configured toperform a precharge operation on the memory die 200. A prechargeoperation may comprise precharging one or more components and/or accesslines of the memory die 200 to one or more predetermined voltage levels.In some instances, the memory cell 205 and/or portions of the memory die200 may be precharged between different access operations. In someinstances, the digit line 215 and/or other components may be prechargedbefore a read operation.

In some examples, the local memory controller 265 may be configured toperform a write operation (e.g., a programming operation) on one or morememory cells 205 of the memory die 200. During a write operation, amemory cell 205 of the memory die 200 may be programmed to store adesired logic state. In some examples, a plurality of memory cells 205may be programmed during a single write operation. The local memorycontroller 265 may identify a target memory cell 205 on which to performthe write operation. The local memory controller 265 may identify atarget word line 210, a target digit line 215, and/or a target plateline 220 in electronic communication with the target memory cell 205(e.g., the address of the target memory cell 205). The local memorycontroller 265 may activate the target word line 210, the target digitline 215, and/or the target plate line 220 (e.g., applying a voltage tothe word line 210, digit line 215, or the plate line 220), to access thetarget memory cell 205. The local memory controller 265 may apply aspecific signal (e.g., voltage) to the digit line 215 and a specificsignal (e.g., voltage) to the plate line 220 during the write operationto store a specific state in the capacitor 240 of the memory cell 205,the specific state being indicative of a desired logic state.

In some examples, the local memory controller 265 may be configured toperform a read operation (e.g., a sense operation) on one or more memorycells 205 of the memory die 200. During a read operation, the logicstate stored in a memory cell 205 of the memory die 200 may bedetermined. In some examples, a plurality of memory cells 205 may besensed during a single read operation. The local memory controller 265may identify a target memory cell 205 on which to perform the readoperation. The local memory controller 265 may identify a target wordline 210, a target digit line 215, and/or a target plate line 220 inelectronic communication with the target memory cell 205 (e.g., theaddress of the target memory cell 205). The local memory controller 265may activate the target word line 210, the target digit line 215, and/ora target plate line 220 (e.g., applying a voltage to the word line 210,the digit line 215, or the plate line 220), to access the target memorycell 205. The target memory cell 205 may transfer a signal to the sensecomponent 250 in response to biasing the access lines. The sensecomponent 250 may amplify the signal. The local memory controller 265may fire the sense component 250 (e.g., latch the sense component) andthereby compare the signal received from the memory cell 205 to thereference signal 255. Based on that comparison, the sense component 250may determine a logic state that is stored on the memory cell 205. Thelocal memory controller 265 may communicate the logic state stored onthe memory cell 205 to the external memory controller 105 (or the devicememory controller) as part of the read operation. The sense component250 may couple with the write circuit after performing the readoperation, to write a logic state back to the memory cell 205. In someexamples, the logic state may be determined at the sense component 250based on one or more inputs from other components (e.g., an I/O bus, thememory cell 205, etc.).

In some examples, voltages on digit lines 215 used for a write operationmay be different (e.g., higher) than voltages on the digit lines 215during a read operation. For example, read operations may result in arelatively small voltage change on the digit lines 215, which may besensed relative to the reference signal 255. However, higher voltages onthe digit lines 215 may be used to write logic states to memory cells205. In some examples, a memory device may be constructed using aprocess that supports multiple types of transistors with differentoperating ranges. For example, a process for implementing FeRAM mayinclude low-voltage and high-voltage transistors, where high-voltagetransistors may have certain characteristics (e.g., thicker gate oxide,wider channels, different doping) that allow for the use of highervoltages before undesired effects may occur (e.g., gate oxide breakdown,source/drain junction breakdown, hot-electron tunneling, etc.). In someexamples, the voltages used for the digit lines 215 for the writeoperation may be higher than the operating range of the low-voltagetransistors of a given process node, and thus read and/or writecircuitry that is involved in generating or maintaining the voltages forthe write operation may employ high-voltage transistors where nodes(e.g., source, gate, drain) of the transistors are exposed to thevoltages seen on the digit lines 215.

In some memory architectures, accessing the memory cell 205 may degradeor destroy the logic state stored in a memory cell 205. For example, aread operation performed on a ferroelectric memory cell may destroy(e.g., deplete) the logic state stored in the ferroelectric capacitor.In another example, a read operation performed in DRAM architectures maypartially or completely discharge the capacitor of the target memorycell. The local memory controller 265 may perform a re-write operationor a refresh operation to return the memory cell to its original logicstate. The local memory controller 265 may re-write the logic state tothe target memory cell after a read operation. In some examples, there-write operation may be considered part of the read operation.Additionally, activating a single access line, such as a word line 210,may disturb the state stored in some memory cells in electroniccommunication with that access line (e.g., in the presence of a voltagedisturbance on a digit line). Thus, a re-write operation or refreshoperation may be performed on one or more memory cells that may not havebeen accessed.

To reduce (e.g., mitigate) voltage disturbances on deselected digitlines 215, memory cells 205 of a memory die 200 may be configured to becouplable with a write circuit including a voltage level shiftercircuit, as described above. A first voltage (e.g., a write voltage) maybe applied to a memory cell 205 via a level shifter circuit, and thelevel shifter circuit may control a slew rate of a first voltage changealong an associated digit line 215. In some examples, the digit line 215may also be grounded through the level shifter circuit, which in someexamples, which may result in a second voltage change along the selecteddigit line 215, where a slew rate of the second voltage change may becontrolled by the level shifter circuit. In some examples, lowering orotherwise adjusting the slew rate of the voltage changes along the digitline 215 may result in lower voltage disturbances along neighboringdigit lines. As such, memory cells 205 coupled with neighboring,deselected digit lines 215 may be unaffected or may not change a logicstate as a result of the lower voltage disturbances.

FIGS. 3A and 3B illustrate examples of non-linear electrical propertiesof a ferroelectric memory cell with hysteresis curves 300-a and 300-b inaccordance with various examples as disclosed herein. Hysteresis curves300-a and 300-b illustrate an example ferroelectric memory cell writingand reading process, respectively. Hysteresis curves 300-a and 300-bdepict the charge, Q, stored on a ferroelectric capacitor (e.g.,capacitor 240 described with reference to FIG. 2) as a function of avoltage difference, V.

A ferroelectric material is characterized by a spontaneous electricpolarization, that is, it maintains a non-zero electric polarization inthe absence of an electric field. Example ferroelectric materialsinclude barium titanate (BaTiO3), lead titanate (PbTiO3), lead zirconiumtitanate (PZT), and strontium bismuth tantalate (SBT). The ferroelectriccapacitors described herein may include these or other ferroelectricmaterials. Electric polarization within a ferroelectric capacitorresults in a net charge at the ferroelectric material's surface andattracts opposite charge through the capacitor terminals. Thus, chargeis stored at the interface of the ferroelectric material and thecapacitor terminals. Because the electric polarization may be maintainedin the absence of an externally applied electric field for relativelylong times, even indefinitely, charge leakage may be significantlydecreased as compared with, for example, capacitors employed in DRAMarrays. This may reduce the need to perform refresh operations.

Hysteresis curves 300-a and 300-b may be understood from the perspectiveof a single terminal of a capacitor. By way of example, if theferroelectric material has a negative polarization, positive chargeaccumulates at the terminal. Likewise, if the ferroelectric material hasa positive polarization, negative charge accumulates at the terminal.Additionally, the voltages in hysteresis curves 300-a and 300-brepresent a voltage difference across the capacitor and are directional.For example, a positive voltage may be realized by applying a positivevoltage to the terminal in question (e.g., a cell plate) and maintainingthe second terminal (e.g., a cell bottom) at ground (or approximatelyzero volts (0V)). A negative voltage may be applied by maintaining theterminal in question at ground and applying a positive voltage to thesecond terminal—i.e., positive voltages may be applied to negativelypolarize the terminal in question. Similarly, two positive voltages, twonegative voltages, or any combination of positive and negative voltagesmay be applied to the appropriate capacitor terminals to generate thevoltage difference shown in hysteresis curves 300-a and 300-b.

As depicted in hysteresis curve 300-a, the ferroelectric material maymaintain a positive or negative polarization with a zero-voltagedifference, resulting in two possible charged states: a charge state 305and a charge state 310. According to the examples of FIGS. 3A and 3B,charge state 305 represents a logic 0 and charge state 310 represents alogic 1. In some examples, the logic values of the respective chargestates may be reversed to accommodate other schemes for operating amemory cell.

A logic 0 or 1 may be written to the memory cell by controlling theelectric polarization of the ferroelectric material, and thus the chargeon the capacitor terminals, by applying voltage. For example, applying anet positive voltage 315 across the capacitor results in chargeaccumulation until charge state 305-a is reached. Upon removing voltage315, charge state 305-a follows path 320 until it reaches charge state305 at zero voltage. Similarly, charge state 310 is written by applyinga net negative voltage 325, which results in charge state 310-a. Afterremoving negative voltage 325, charge state 310-a follows path 330 untilit reaches charge state 310 at zero voltage. Charge states 305-a and310-a may also be referred to as the remnant polarization (Pr) values,i.e., the polarization (or charge) that remains upon removing theexternal bias (e.g., voltage). The coercive voltage is the voltage atwhich the charge (or polarization) is zero.

To read, or sense, the stored state of the ferroelectric capacitor, avoltage may be applied across the capacitor. In response, the storedcharge, Q, changes, and the degree of the change depends on the initialcharge state—i.e., the final stored charge (Q) depends on whether chargestate 305-b or 310-b was initially stored. For example, hysteresis curve300-b illustrates two possible stored charge states 305-b and 310-b.Voltage 335 may be applied across the capacitor 240 as discussed withreference to FIG. 2. In other examples, a fixed voltage may be appliedto the cell plate and, although depicted as a positive voltage, voltage335 may be negative. In response to voltage 335, charge state 305-b mayfollow path 340. Likewise, if charge state 310-b was initially stored,then it follows path 345. The final position of charge state 305-c andcharge state 310-c depend on one or more factors, including the specificsensing scheme and circuitry.

In some examples, the final charge may depend on the intrinsiccapacitance of the digit line connected to the memory cell. For example,if the capacitor is electrically connected to the digit line and voltage335 is applied, the voltage of the digit line may rise due to itsintrinsic capacitance. A voltage measured at a sense component may notequal voltage 335 and instead may depend on the voltage of the digitline. The position of final charge states 305-c and 310-c on hysteresiscurve 300-b may thus depend on the capacitance of the digit line and maybe determined through a load-line analysis—i.e., charge states 305-c and310-c may be defined with respect to the digit line capacitance. As aresult, the voltage of the capacitor, voltage 350 or voltage 355, may bedifferent and may depend on the initial state of the capacitor.

By comparing the digit line voltage to a reference voltage, the initialstate of the capacitor may be determined. The digit line voltage may bethe difference between voltage 335 and the final voltage across thecapacitor, voltage 350 or voltage 355—i.e., the difference between thevoltage 335 and the voltage 350 or the difference between the voltage335 and the voltage 355. A reference voltage may be generated such thatits magnitude is between the two possible voltages of the two possibledigit line voltages to determine the stored logic state—i.e., if thedigit line voltage is higher or lower than the reference voltage. Uponcomparison by the sense component, the sensed digit line voltage may bedetermined to be higher or lower than the reference voltage, and thestored logic value of the ferroelectric memory cell (i.e., a logic 0or 1) may be determined. In some cases, a sense component may integratecharge read from the capacitor and may output an integrated charge levelto determine the stored logic value of the ferroelectric memory cell.

In some examples, a ferroelectric memory cell may maintain the initiallogic state after a read operation. For example, if charge state 305-bis stored, the charge state may follow path 340 to charge state 305-cduring a read operation and, after removing voltage 335, the chargestate may return to initial charge state 305-b by following path 340 inthe opposite direction. In some examples, a ferroelectric memory cellmay lose its initial logic state after a read operation. For example, ifcharge state 310-b is stored, the charge state may follow path 345 tocharge state 305-c during a read operation and, after removing voltage335, the charge state may relax to the charge state 305-b by followingpath 340.

Hysteresis curve 300-b illustrates an example of reading a memory cellthat is configured to store the charge state 305-b and the charge state310-b. A read voltage 335 may be applied, for example, as a voltagedifference via a digit line 215 and a plate line 220 as described withreference to FIG. 2. Hysteresis curve 300-b may illustrate readoperations where the read voltage 335 is a negative voltage differenceVcap (e.g., where Vbottom−Vplate is negative). A negative read voltageacross the capacitor may be referred to as a “plate high” readoperation, where a plate line 220 is taken initially to a high voltage,and a digit line 215 is initially at a low voltage (e.g., a groundvoltage). Although read voltage 335 is shown as a negative voltageacross the ferroelectric capacitor 240, in alternative operations a readvoltage may be a positive voltage across the ferroelectric capacitor240, which may be referred to as a “plate low” read operation.

The read voltage 335 may be applied across the ferroelectric capacitor240 when a memory cell 205 is selected (e.g., by activating a switchingcomponent 245 as described with reference to FIG. 2). Upon applying theread voltage 335 to the ferroelectric capacitor 240, charge may flowinto or out of the ferroelectric capacitor 240 via the digit line 215and plate line 220, and different charge states may result depending onwhether the ferroelectric capacitor 240 was at charge state 305-a (e.g.,a logic 1) or at charge state 310-a (e.g., a logic 0).

FIG. 4 illustrates an example of a memory device 400 that supportsaccess line disturbance mitigation in accordance with examples asdisclosed herein. Memory device 400 may include word lines 210, digitlines 215, and an array of memory cells (e.g., including memory cell 405and memory cells 410). In some examples, memory device 400 may be anexample of a cross-point architecture, a pillar architecture, or aplanar architecture. Memory device 400 may be an example of or include amemory die 200, as described with reference to FIG. 2. In some examples,memory device 400 may implement a memory cell selection procedure aspart of a read or write operation, as described with reference to FIGS.1-3.

Memory device 400 may implement a selection procedure to select a memorycell 405 (e.g., or multiple memory cells 405), where memory cell 405 maybe located at an intersection of a word line 210-b and a digit line215-b. In some examples, word line 210-b and digit line 215-b mayadditionally or alternatively be referred to as selected word line 210-band selected digit line 215-b. Other word lines 210 (e.g., word lines210-a and 210-c) may be referred to as unselected word lines 210 ordeselected word lines 210, while other digit lines 215 (e.g., digitlines 215-a and 215-c) may be referred to as unselected digit lines 215or deselected digit lines 215.

In some examples, memory device 400 may select memory cell 405 byapplying a voltage to selected word line 210-b and applying a voltage toselected digit line 215-b (e.g., via a selection component). The voltageapplied to word line 210-b may activate switching components 420-a,420-b, and 420-c, and thereby couple digit lines 215-a, 215-b, and 215-cto memory cells 410-a, 405, and 410-c, respectively. The voltage appliedto digit line 215-b may be used to read, write, or perform otherfunctions on memory cell 405 while digit line 215-b is coupled withmemory cell 405.

In some examples, memory device 400 may deselect other digit lines 215(e.g., digit line 215-a and 215-c) between selected digit lines (e.g.,digit line 215-b). For example, digit lines 215-a and 215-c may bedeselected by activating shunts 425-a and 425-c to couple digit lines215-a and 215-c with a plate 415, where the plate 415 may be coupledwith or be an example of plate lines as described with reference to FIG.2. Plate 415 may be coupled with a top plate 430 of each memory cell(e.g., memory cell 405 and memory cells 410), such that the top plate430 of each memory cell may be at a same voltage as plate 415. Ifdeselected digit lines 215-a and 215-c are coupled with the plate 415(e.g., via shunts 425-a and 425-c), the deselected digit lines 215 mayalso be at a same voltage as the plate 415. As such, the voltagedifference across memory cells 410 (e.g., from the top plate 430 to abottom plate 435) may be zero (e.g., because the plate 415 is coupledwith the top plate 430 and the digit line 215 is coupled with the bottomplate 435, and both are at the same voltage). In some examples,maintaining a zero voltage across memory cells 410-a and 410-b mayprevent disturbances to memory cells 410-a and 410-b (e.g., changes in alogic state of memory cells 410) when performing an access operation onmemory cell 405. In some examples, the deselected digit lines 215 mayact as a shield for any selected digit lines (e.g., digit line 215-b)during an access operation (e.g., read operation, write operation,etc.).

In some examples, a change in voltage on digit line 215-b (e.g., as aresult of cell selection or activation procedures) may cause voltagedisturbances on digit line 215-a, 215-c, or both. Such disturbances maycause the voltage difference across memory cell 410-a and/or 410-b to benon-zero for a period of time (e.g., until the voltage of digit line215-a and/or 215-c equalizes with the voltage of plate 415). In someexamples, memory device 400 may be configured with longer digit lines215, for example, to realize one or more benefits (e.g., to provide areafor one or more circuits, to increase a density of a memory device). Thelonger digit lines 215 may have a larger capacitance (e.g., whencompared with non-lengthened digit lines 215), and applying or removinga voltage from such a digit line 215 may cause voltage disturbances inneighboring digit lines 215. For example, applying or removing a voltagefrom selected digit line 215-b may capacitively couple digit line 215-bwith one or more deselected digit lines 215 (e.g., may form a bridge),such that if a voltage on digit line 215-b goes high or low, a voltageon the one or more deselected digit lines 215 may go high or low (e.g.,transiently), respectively. Such disturbances in the voltage ondeselected digit lines 215 (e.g., digit lines 215-a and 215-c) mayimpact a logic state of coupled memory cells 410 via a cumulativehammering effect that may occur over multiple voltage changes.

To reduce (e.g., mitigate) voltage disturbances on deselected digitlines 215, memory cells of memory device 400 (e.g., memory cell 405 andmemory cells 410) may be configured to be couplable with a write circuitincluding a voltage level shifter circuit. For example, the changes involtage on digit line 215-b may be controlled via a voltage levelshifter circuit of a write circuit associated with memory cell 405. Insome examples, the write circuit may be coupled with a sense component(e.g., a latch) used to sense a logic state of memory cell 405 during aread operation. The write circuit may be configured to write a logicstate to memory cell 405 (e.g., a same logic state as previously storedon memory cell 405 or a different logic state) after completing the readoperation. A first voltage (e.g., a write voltage) may be applied tomemory cell 405 via a level shifter circuit (e.g., a dynamic levelshifter circuit), and the level shifter circuit may control a slew rateof the first voltage change along digit line 215-b (e.g., to bring digitline 215-b to the write voltage). For example, the slew rate of thewrite voltage may be controlled via a current mirror circuit (e.g.,current driver circuit or current follower circuit) coupled with apull-up circuit of the dynamic level shifter circuit. The current mirrorcircuit may control a voltage or a current applied to the pull-upcircuit. In some examples, lowering or otherwise adjusting the slew rateof the first voltage change along digit line 215-b may result in lowervoltage disturbances along digit lines 215-a and/or 215-c.

Digit line 215-b may also be grounded through the dynamic level shiftercircuit. In some examples, grounding digit line 215-b may apply a writevoltage to digit line 215-b. In some examples, grounding digit line215-b may remove a write voltage (e.g., the first voltage) from digitline 215-b, which may result in a second voltage change along digit line215-b. The slew rate of the second voltage change may be controlled viaa current driver circuit coupled with a pull-down circuit of the dynamiclevel shifter circuit (e.g., by controlling a voltage or current appliedto the pull-down circuit). Controlling the slew rate of the secondvoltage change may result in lower voltage disturbances along digitlines 215-a and/or 215-c, as described above. As such, memory cellscoupled with digit lines 215-a and/or 215-c may be unaffected or may notchange a logic state as a result of the lower voltage disturbances. Insome examples, adjusting the slew rates of the first and second voltagechanges may result in a small impact to cell programming times, due tocell kinetics.

FIG. 5A illustrates an example of a circuit diagram 501 that supportsaccess line disturbance mitigation in accordance with examples asdisclosed herein. Circuit diagram 501 illustrates a word line 210, adigit line 215, a plate line 220, and additional components that may becoupled with a memory cell 505. Circuit diagram 501 may representportions of a sense circuit and a write circuit used for accessoperations, such as a read or write operation as described withreference to FIGS. 1-4. For example, circuit diagram 501 may illustratea write circuit that may control a slew rate of one or more voltagechanges along a selected digit line 215 to reduce (e.g., mitigate)voltage disturbances to neighboring digit lines 215, as described withreference to FIG. 4. In some examples, during read or write operationsassociated with the selected digit line 215, the circuit illustrated incircuit diagram 501 may be selectively coupled with the selected digitline 215 and may be decoupled from other (e.g., neighboring) digit lines215.

Memory cell 505 may be accessed or selected by applying a voltage to aword line 210-d to activate a switching component (e.g., switchingcomponent 420-d) and couple a selected digit line 215-d to memory cell505. One or more voltages may be applied to digit line 215-d and to aplate line 220-a to perform an access operation (e.g., read, write,etc.) on memory cell 505. Memory cell 505 may be coupled with a sensecircuit that includes an amplification component 520 and a sensecomponent 515 (e.g., a latch) configured to sense a logic state ofmemory cell 505 via a voltage of digit line 215-d (e.g., as part of aread operation). Memory cell 505 may also be coupled with a writecircuit that includes a level shifter circuit 525 (e.g., dynamic levelshifter circuit 525-a), the write circuit being configured to write alogic state to memory cell 505 via a voltage of digit line 215-d (e.g.,as part of a write or a write-back operation). In some examples, asillustrated, one or more portions of the write circuit may be coupledwith one or more portions of the sense circuit.

Amplification component 520 and sense component 515 may be operated byapplying a first supply voltage 532 (e.g., a peripheral circuitryvoltage (V_(PERI))), which in some examples, may enable amplificationcomponent 520 and sense component 515 to include transistors having asmaller gate oxide thickness (e.g., to be a thin oxide device) becausethey are not subject to voltages in excess of V_(PERI). Use of thin gatedevices for substantial portions of amplification component 520 andsense component 515 may improve performance of an amplifier ofamplification component 520, and may provide a higher latch offset forsense component 515. In some examples, amplification component 520 andsense component 515 may include one or more switching components 510(e.g., transistors) that may be operable to selectively coupleamplification component 520 and sense component 515 with the local digitline 512 and write circuit, a memory controller, or other components ofa memory device.

For a read operation of memory cell 505, digit line 215-d may be coupledwith local digit line 512 via a shunt (e.g., shunt transistor 425-d)while other digit lines (e.g., digit line 215-e) may be decoupled withlocal digit line 512 via a shunt (e.g., transistor 425-e). Amplificationcomponent 520 may be coupled with local digit line 512 via switchingcomponent 510-g and may be initialized by asserting a precharge voltagePRECH 522, which may initialize differential amplifier 521 (e.g., to abias voltage VBAS) for sensing charge on digit line 215-d. For example,then PRECH 522 is asserted, the negative input node and the output nodeof differential amplifier 521 may be coupled with V_(BIAS), which may beselected to be substantially equal to a threshold voltage for thin oxidedevices. The positive input node of differential amplifier 521 may beset to a reference voltage VREF which may be, for example, a groundvoltage or 0V. PRECH 522 may then be deasserted and word line 210-d maybe asserted. When PRECH 522 is deasserted, the negative input node andthe output node of the differential amplifier 521 may be coupled via acapacitor, which may integrate charge from memory cell 505 when thenegative input node of the differential amplifier 521 is coupled withthe digit line 215-d via switching component 510-g.

Amplification component 520 may thus integrate charge read from memorycell 505 via digit line 215-d after word line 210-d is activated and mayoutput an integrated charge level that may be lower than VBAS (e.g.,when memory cell 505 is in a first state) or higher than VBAS (e.g.,when memory cell 505 is in a second state). Sense component 515 may becoupled with amplification component 520 via switching component 510-f,and once the first supply voltage 532 is applied (e.g., via switch 531),sense component 515 may latch the sensed logic state of memory cell 505at NodeA 516 and NodeB 517. For example, if the output of amplificationcomponent 520 is higher than a threshold voltage of the latch circuit ofsense component 515 when the supply voltage 532 is applied, NodeA 516may latch a voltage corresponding to the first supply voltage 532, whileif the output of amplification component 520 is lower than the thresholdvoltage of the latch circuit of sense component 515 when the supplyvoltage 532 is applied, NodeA 516 may latch a voltage corresponding to aground voltage or 0V. NodeA 516 may correspond to an inverted logicstate of the stored logic state on memory cell 505 while NodeB 517 maycorrespond to the non-inverted logic state of the stored logic state onmemory cell 505. Once a voltage has been acquired from memory cell 505(e.g., sensed by amplification component 520 and latched in sensecomponent 515), switching components 510-g and/or 510-f may switch off.

One or more of switching components 510-a and 510-b may also beactivated to couple sense component 515 to an I/O bus (e.g., coupledwith a memory controller) to output a logic state (e.g., inverted ornon-inverted) of data resulting from a read operation of memory cell505. One of switching components 510-c or 510-d may be activated tocouple sense component 515 with the write circuit based on a determinedlogic state to be written to memory cell 505. In one example, switchingcomponent 510-c may be activated to write a logic state to memory cell505 corresponding to the logic state previously stored on memory cell505 (e.g., writing back a non-inverted logic state), while switchingcomponent 510-d may be activated to write a different logic state tomemory cell 505 (e.g., a flipped or opposite logic state). Some of theswitching components 510 may be subject to voltages exceeding theoperating range for thin gate transistors, and thus may be thick gatedevices. For example, switching components 510-c, 510-d, 510-e, and510-g may experience voltages higher than V_(PERI) on one or more nodes(e.g., source, gate, drain), and may thus be thick gate devices.Switching components 510-a, 510-b, and 510-f on the other hand may notexperience voltages in excess of V_(PERI), and may thus be thin gatedevices. Other switching components having one or more nodes coupleddirectly to digit line 215-d or local digit line 512 (e.g., shunttransistors 425-d or 425-e, switching component 420-d) may also be thickgate devices.

The write circuit may be configured with a level shifter circuit 525-a,where the determined logic state may be written to memory cell 505 viathe level shifter circuit 525-a. As described with reference to FIG. 4,the level shifter circuit 525-a may control a slew rate of a writevoltage applied to and removed from memory cell 505 (e.g., as part of awrite operation). The level shifter circuit 525-a may include a pull-upcircuit 530-a (e.g., a positive metal oxide semiconductor (PMOS)transistor) coupled with a current mirror circuit 540-a (e.g., wherecurrent mirror circuit 540-a and pull-up circuit 530-a make a currentdriver circuit) that may control a gate of the pull-up circuit 530-a viaa voltage V_(PBIAS) 545. The pull-up circuit 530-a may be coupled withthe write circuit via an inverter, such that a second supply voltageV_(MSA) 550 may be applied to digit line 215-d via the dynamic levelshifter circuit 525-a. The dynamic level shifter circuit 525-a may beconfigured such that current mirror circuit 540-a may control V_(PBIAS)545, which may control a current and/or voltage through the pull-upcircuit 530-a and enable the dynamic level shifter circuit 525-a tocontrol a slew rate when applying V_(MSA) 550 to memory cell 505.

The dynamic level shifter circuit 525-a may also include a pull-downcircuit 535-a (e.g., an negative metal oxide semiconductor (NMOS)transistor) coupled with a current mirror circuit 540-b (e.g., a currentdriver circuit) that may control an gate of the pull-down circuit 535-avia a voltage V_(NBIAS) 555. The pull-down circuit 535-a may be coupledwith the write circuit via an inverter, such that a write voltage (e.g.,V_(MSA) 550 or ground) may be applied to or removed from digit line215-d via the dynamic level shifter circuit 525-a. The dynamic levelshifter circuit 525-a may be configured such that current mirror circuit540-b may control V_(NBIAS) 555, which may control a current and/orvoltage through the pull-down circuit 535-a and enable the dynamic levelshifter circuit 525-a to control a slew rate when driving digit line215-d to a ground voltage.

Level shifter circuit 525-a may be configured to shift a write voltagefrom V_(PERI) 532 to V_(MSA) 550 (e.g., using the inverter and pull-upcircuit 530-a or pull-down circuit 535-a). This may enable the sensecomponent 515 to operate using V_(PERI) 532, while writing to memorycell 505 using V_(MSA) 550, where V_(MSA) 550 may be higher thanV_(PERI) 532. As described above, operating the sense component 515using V_(PERI) 532 (e.g., a lower voltage) may allow the sense component515, or the transistors of the sense component 515, to have a smallergate oxide thickness and provide a higher latch offset. Similarly,operating level shifter circuit 525-a using V_(MSA) 550 may enabledynamic level shifter circuit 525-a and associated circuitry (e.g.,transistors) to employ higher voltages. In some examples, level shiftercircuit 525-a may shift a write voltage from V_(PERI) 532 to V_(MSA) 550using a dynamic node 560-a.

For example, switching component 510-e may be activated before writing alogic state to memory cell 505, while V_(PBIAS) 545 and V_(NBIAS) 555are deasserted (e.g., V_(PBIAS) may equal V_(MSA) while V_(NBIAS) may beat a ground state). Switching component 510-e may be activated and thendeactivated to couple node 560-a with the V_(MSA) voltage source, suchthat node 560-a may be brought to V_(MSA) 550 and then left floating.The state of node 560-a at a voltage V_(MSA) 550 may be referred to as ahigh-Z state.

If a logic state corresponding to ‘0’ was read from memory cell 505 viaamplification component 520 and sense component 515, NodeA 516 may latcha voltage corresponding to V_(PERI). If a non-inverting logic state isto be written to memory cell 505, switching component 510-c may beactivated, which may not affect the voltage (e.g., negligibly affect thevoltage) of node 560-a, because the gate of switching component 510-cmay also be at V_(PERI) and thus both gate to source and gate to drainvoltages of switching component 510-c may be below a threshold voltage.As such, node 560-a may remain at or nearly at V_(MSA) 550 and thepull-down circuit 535-a (e.g., the NMOS of the pull-down circuit 535-a)may be activated (e.g., by activation of V_(NBIAS) and V_(PBIAS)) toapply a ground voltage to memory cell 505 via digit line 215-d. Whengrounding digit line 215-d, current mirror circuit 540-b may control thevoltage and/or current through the pull-down circuit 535-a, such thatthe slew rate may be regulated (e.g., lowered) and disturbances onneighboring digit lines 215 may be reduced. In some examples, dynamiclevel shifter circuit 525-a may maintain digit line 215-d at grounduntil the write operation is completed.

Alternatively, if a logic state corresponding to ‘1’ was read frommemory cell 505 via amplification component 520 and sense component 515,NodeA 516 may latch a ground voltage. Switching component 510-e may beactivated and then deactivated to couple node 560-a with the V_(MSA)voltage source, such that node 560-a may be brought to V_(MSA) 550 andthen left floating. In this case, when switching component 510-c isactivated, dynamic node 560-a may be pulled to ground via switchingcomponent 510-c. As such, the pull-up circuit 530-a (e.g., the PMOS ofthe pull-up circuit 530-a) may be activated (e.g., by activatingV_(PBIAS) and V_(NBIAS)) to apply V_(MSA) 550 to memory cell 505 viadigit line 215-d. When applying V_(MSA) 550 to digit line 215-d, currentmirror circuit 540-a may control the voltage and/or current through thepull-up circuit 530-a, such that the slew rate may be regulated (e.g.,lowered) and disturbances on neighboring digit lines 215 may be reduced.Once the write operation on memory cell 505 is completed, switchingcomponent 510-c may be deactivated and switching component 510-e may beactivated to couple node 560-a with the V_(MSA) voltage source. Withnode 560-a at V_(MSA) 550, the pull-up circuit 530-a (e.g., the PMOS ofthe pull-up circuit 530-a) may be deactivated, and the pull-down circuit535-a (e.g., the NMOS of the pull-down circuit 535-a) may be activatedto apply ground and discharge digit line 215-d. When grounding digitline 215-d, current mirror circuit 540-b may control the voltage and/orcurrent through the pull-down circuit 535-a, such that the slew rate maybe regulated (e.g., lowered) and disturbances on neighboring digit lines215 may be reduced When the digit line 215-d has been discharged and theword line 210-d deactivated, V_(NBIAS) and V_(PBIAS) may be deactivated,which may leave level shifter circuit 525-a in a high-impedance statesuch that the next read operation (e.g., on a next row or differentdigit line 215) can be performed using amplification component 520 andsense component 515.

As described above, switching component 510-d may be used to write backan inverted logic state to memory cell 505, with the state of dynamicnode 560-a being determined by NodeB 517 (the inverse of NodeA 516) andthe operations of level shifter circuit 525-a being similar to thatdescribed above.

In some examples, to reduce the possibility of node 560-a floating toground when NodeA is at V_(PERI), a half latch configuration may becoupled with node 560-a, as described with reference to FIG. 5B.

FIG. 5B illustrates an example of a circuit diagram 502 that supportsaccess line disturbance mitigation in accordance with examples asdisclosed herein. Circuit diagram 502 may be coupled with one or morecomponents represented in circuit diagram 501, and may includeadditional components compared to circuit diagram 501. Circuit diagram502 may represent portions of a write circuit coupled with a sensecircuit used for access operations, such as a read or write operation asdescribed with reference to FIGS. 1-5A. For example, circuit diagram 502may illustrate a write circuit including a level shifter circuit 525(e.g., dynamic level shifter circuit 525-b) configured to control a slewrate of one or more voltage changes along a selected digit line 215 toreduce (e.g., mitigate) voltage disturbances to other digit lines 215,as described with reference to FIGS. 4 and 5A.

Circuit diagram 502 may couple with or represent one or more portionscorresponding to circuit diagram 501. For example, node 560-b may be anexample of a node 560 or dynamic level shifter circuit 525-b may be anexample of a dynamic level shifter circuit 525, described with referenceto FIG. 5A. In some examples, dynamic level shifter circuit 525-b mayinclude a pull-up circuit 530-b and a pull-down circuit 535-b, which mayeach be coupled with a current mirror circuit (e.g., current drivercircuit) to control a current and/or voltage through the respectivecircuit, as described with reference to FIG. 5A. Circuit diagram 502 mayalso include a local digit line 512-a, which may be an example of or becoupled with local digit line 512 described with reference to FIG. 5A.Circuit diagram 502 may additionally include a half latch 565-a, whichmay enable node 560-b to avoid floating when not pulled to ground viaswitching component 510-c or switching component 510-d, as describedwith reference to FIG. 5A.

Half latch 565-a may include a switching component 510-i (e.g., a PMOS)and switching component 510-j (e.g., a PMOS), where switching component510-j may be coupled with switching component 510-i, with a voltagesource at V_(MSA) 550, and with local digit line 512-a. As describedwith reference to FIG. 5A, a write procedure may be performed on amemory cell coupled with local digit line 512-a. Prior to the writeprocedure, node 560-b may be at a voltage V_(MSA) 550 (e.g., byasserting switching component 510-h) and then left floating (e.g., whenwriting a logic “0” to the memory cell). In some examples, node 560-bmay continue to float during the write procedure, and may drift to anunknown state, which may cause errors in the write procedure. Half latch565-a may be used to bias node 560-b during the write procedure byactivating switching component 510-i to couple node 560-b to V_(MSA) 550once the write voltage is established on local digit line 512-a As such,node 560-b may be maintained at V_(MSA) 550 during a write portion ofthe write procedure and may be left floating during a time it takes toactivate switching component 510-c or 510-d of FIG. 5A and establish thewrite voltage on local digit line 512-a.

FIGS. 6A and 6B illustrate examples of timing diagrams 601 and 602 thatsupport access line disturbance mitigation in accordance with examplesas disclosed herein. Timing diagrams 601 and 602 illustrate proceduresduring a read operation and a corresponding write operation (e.g.,rewrite operation). The read operation may correspond to a time periodbetween t0 and t3 that includes an initial phase 620 through a secondphase 630. The write operation may correspond to a time period betweent3 and t7 that includes a third phase 635 through a sixth phase 650.Timing diagrams 601 and 602 show various voltage levels associated withcomponents of the circuits depicted in circuit diagrams 501 and 502 anddescribed with reference to FIG. 5. Timing diagrams 601 and 602 may alsoshow voltage levels associated with one or more components of a memorydevice, which may be an example of memory device 400 described withreference to FIG. 4. Timing diagrams 601 and 602 may illustratetechniques for memory cell read and write procedures that may reducedisturbances on neighboring digit lines not included in the read andwrite procedures.

For example, timing diagrams 601 and 602 may illustrate methods foradjusting a slew rate (e.g., lowering a slew rate) of a voltage appliedto a selected digit line (e.g., digit line voltage (V_(DL)) 615), wherethe adjusted slew rate may reduce disturbances on neighboring digitlines. Timing diagrams 601 and 602 include V_(DL) 615, a voltage appliedto a selected word line (e.g., word line voltage (V_(WL)) 610), and avoltage applied to a plate line (e.g., plate line voltage (V_(PL)) 605),where the selected digit line, and the selected word line, and plateline may correspond to portions of the memory device 400 or circuitdiagrams 501 and/or 502.

During the initial phase 620 (e.g., beginning at t0), which may also bereferred to as an idle period, the selected bit line and the selectedword line may be kept at a constant voltage (e.g., at or near groundvoltage (V_(GND))). During phase 620, V_(PL) 605 may be driven to avoltage (e.g., V_(PERI)) that may be lower than V_(MSA) (e.g., a writevoltage). The plate line may initialize an associated memory cell for aread and write procedure by biasing a first plate of a memory cell suchthat a second plate of the cell coupled with the digit line may rise toa voltage based on a logic state stored in the memory cell. As such,initial phase 620 may be referred to as a digit line initializationphase. At or after t0, a switching component connecting the digit lineto a sense amplifier may be activated, such that the voltage on thedigit line may be amplified by the sense amplifier.

At t1, a first phase 625 may begin, which may be referred to as a signaldevelopment phase. At or after t1, V_(WL) 610 may be driven to anactivation voltage (V_(ACT)) to activate a switching component andcouple the digit line with the memory cell (e.g., where the digit linemay already be coupled with the sense amplifier). V_(DL) 615 may remainat or near V_(GND) during first phase 625, although a small differencein V_(DL) 615 that depends on the logic state stored in the memory cellmay be detected by the amplification component.

At t2, a second phase 630 may begin, which may be referred to as a sensestage. At or after t2, V_(PL) 605 may be removed from its drivingvoltage and may begin falling back to V_(GND). At or after t2, anisolator switching component may activate to couple the sense amplifier(e.g., amplification component 520) to a sense component (e.g., sensecomponent 515). As such, a voltage based on the logic state stored onthe memory cell and sensed via the digit line and the sense amplifier(e.g., which may determine the logic state based on comparing thevoltage developed on the digit line with a reference voltage) may belatched (e.g., a voltage of either V_(PERI) or ground may be latched)within the sense component. During the second phase 630, the switchingcomponent coupling the sense amplifier to the digit line may also bedeactivated to decouple the two components. One or more components ofthe sense component may activate to determine the logic state of thememory cell based on the voltage developed on the sense amplifier.

At t3, the write operation may begin with a third phase 635, where thirdphase 635 may be referred to as a digit line charge stage. At or aftert3, the isolator switching component may activate to isolate (e.g.,decouple) the sense component from the sense amplifier. At or after t3,a switching component coupling a level shifter circuit node to a voltagesource may be activated, such that the node may be driven to a voltageof the voltage source (e.g., V_(MSA)). A voltage may also be applied toactivate a pull-down circuit associated with the level shifter circuit.At or after t3, one of two switching components coupling the levelshifter circuit to the sense component may be activated, such that thedigit line may be coupled with a voltage source (e.g., V_(MSA)) or aground (e.g., V_(GND)) via the level shifter circuit. The voltageapplied to the digit line may be based on which of the two switchingcomponents is activated, which may, in turn, be based on a logic stateto write back to the memory cell.

In a first example, the logic state to write back to the memory cell maybe a “1” and the digit line may be coupled with the voltage source viathe level shifter circuit, such that V_(DL) 615-a is driven to thevoltage of the voltage source (e.g., V_(MSA)). A slew rate of thevoltage change of V_(DL) 615-a may be controlled by a current mirrorcircuit (e.g., current driver circuit) coupled with a pull-up circuit ofthe level shifter circuit, as described with reference to FIG. 5A. Insome examples, as illustrated in timing diagram 602, the slew rate ofV_(DL) 615 may be lowered, such that a V_(DL) 615-c may reach V_(MSA)slower than V_(DL) 615-a (e.g., third phase 635 may be longer in timingdiagram 602). In a second example, the logic state to write back to thememory cell may be a “0” and the digit line may be coupled with theground, such that V_(DL) 615-b is driven to or maintained at the voltageof the ground (e.g., V_(GND)).

At t4, a fourth phase 640 may begin, which may be referred to as a writeback stage. At or around t4, V_(DL) 615 may reach a write voltage (e.g.,V_(MSA) or V_(GND)) and may maintain the write voltage for the durationof fourth phase 640 (e.g., or for most of the fourth phase 640). Duringfourth phase 640, the logic state may be written to the memory cell bythe application of the write voltage.

At t5, a fifth phase 645 may begin, which may be referred to as a digitline discharge stage. At or after t5, components of the sense componentsmay be deactivated by removing a voltage from the correspondingcomponents. The switching components coupling the level shifter circuitnode to the voltage source (e.g., V_(MSA)) and coupling the levelshifter circuit to the sense component may also be deactivated. As such,the write voltage may be removed from the digit line via the levelshifter circuit and the ground. In a first example, V_(DL) 615-a mayfall from V_(MSA) to V_(GND), where a slew rate of the voltage change ofV_(DL) 615-a may be controlled by a current mirror circuit (e.g.,current driver circuit) coupled with a pull-down circuit of the levelshifter circuit, as described with reference to FIG. 5A. In someexamples, as illustrated in timing diagram 602, the slew rate of V_(DL)615 may be lowered, such that a V_(DL) 615-c may reach V_(GND) slowerthan V_(DL) 615-a (e.g., fifth phase 645 may be longer in timing diagram602). In a second example, the digit line may already be coupled withthe ground, such that V_(DL) 615-b is driven to or maintained at thevoltage of the ground (e.g., V_(GND)).

At t6, a sixth phase 650 may begin and the discharging of the digit linemay be completed. At or after t6, the pull-down circuit may bedeactivated. At or after t6, V_(ACT) may be removed from the word line(e.g., the word line may be deselected), such that V_(WL) 610 may fallfrom V_(ACT) to V_(GND) or a voltage close to V_(GND) at or before t7.In some examples, the word line may not be deselected until after thedigit line is discharged.

FIG. 7 shows a block diagram 700 of a memory device 705 that supportsaccess line disturbance mitigation in accordance with examples asdisclosed herein. The memory device 705 may be an example of aspects ofa memory device as described with reference to FIGS. 4-6. The memorydevice 705 may include a read component 710, a coupling component 715, awrite component 720, and a slew rate component 725. Each of thesemodules may communicate, directly or indirectly, with one another (e.g.,via one or more buses).

The read component 710 may read a first logic state of a ferroelectricmemory cell, the reading including coupling a sense circuit to a digitline associated with the ferroelectric memory cell and latching, at thesense circuit, a first voltage or a second voltage. In some examples,reading the first logic state includes comparing a voltage generated onthe digit line based on the ferroelectric memory cell with a referencevoltage.

The coupling component 715 may decouple the sense circuit from the digitline based on latching the first voltage or the second voltage. In someexamples, the coupling component 715 may couple the sense circuit with awrite circuit based on latching the first voltage or the second voltage.In some examples, the coupling component 715 may selectively couple thedigit line associated with the ferroelectric memory cell with the sensecircuit for reading the first logic state and writing the second logicstate.

The write component 720 may write a second logic state back to theferroelectric memory cell, the writing including driving the digit lineto a third voltage or a fourth voltage for a write back operationfollowing reading the first logic state, where at least one of the thirdvoltage or the fourth voltage is different than the first voltage andthe second voltage. In some examples, the write component 720 may writea second logic state to the ferroelectric memory cell, the writingincluding controlling a first slew rate of the digit line for drivingthe digit line to a third voltage that is higher than the first voltageor the second voltage.

In some examples, writing the second logic state includes selecting thesecond logic state to be the same as the first logic state. In someexamples, writing the second logic state includes inverting the firstlogic state to obtain the second logic state. In some examples, thefirst logic state is the same as the second logic state. In someexamples, the first logic state is different than the second logicstate.

The slew rate component 725 may control a first slew rate of the digitline when applying the third voltage. In some examples, the slew ratecomponent 725 may control a current sourced to the digit line whenapplying the third voltage. In some examples, the slew rate component725 may control a second slew rate of the digit line when driving thedigit line from the third voltage to the fourth voltage. In someexamples, the slew rate component 725 may control a current removed fromthe digit line when driving the digit line from the third voltage to thefourth voltage. In some examples, writing the second logic state to theferroelectric memory cell includes controlling, after driving the digitline to the third voltage, a second slew rate of the digit line fordriving the digit line from the third voltage to a fourth voltage.

FIG. 8 shows a flowchart illustrating a method or methods 800 thatsupports access line disturbance mitigation in accordance with aspectsof the present disclosure. The operations of method 800 may beimplemented by a memory device or its components as described herein.For example, the operations of method 800 may be performed by a memorydevice as described with reference to FIG. 7. In some examples, a memorydevice may execute a set of instructions to control the functionalelements of the memory device to perform the described functions.Additionally or alternatively, a memory device may perform aspects ofthe described functions using special-purpose hardware.

At 805, the memory device may read a first logic state of aferroelectric memory cell, the reading including coupling a sensecircuit to a digit line associated with the ferroelectric memory celland latching, at the sense circuit, a first voltage or a second voltage.The operations of 805 may be performed according to the methodsdescribed herein. In some examples, aspects of the operations of 805 maybe performed by a read component as described with reference to FIG. 7.

At 810, the memory device may decouple the sense circuit from the digitline based on latching the first voltage or the second voltage. Theoperations of 810 may be performed according to the methods describedherein. In some examples, aspects of the operations of 810 may beperformed by a coupling component as described with reference to FIG. 7.

At 815, the memory device may write a second logic state back to theferroelectric memory cell, the writing including driving the digit lineto a third voltage or a fourth voltage for a write back operationfollowing reading the first logic state, where at least one of the thirdvoltage or the fourth voltage is different than the first voltage andthe second voltage. The operations of 815 may be performed according tothe methods described herein. In some examples, aspects of theoperations of 815 may be performed by a write component as describedwith reference to FIG. 7.

In some examples, an apparatus as described herein may perform a methodor methods, such as the method 800. The apparatus may include features,means, or instructions (e.g., a non-transitory computer-readable mediumstoring instructions executable by a processor) for reading a firstlogic state of a ferroelectric memory cell, the reading includingcoupling a sense circuit to a digit line associated with theferroelectric memory cell and latching, at the sense circuit, a firstvoltage or a second voltage, decoupling the sense circuit from the digitline based on latching the first voltage or the second voltage, andwriting a second logic state back to the ferroelectric memory cell, thewriting including driving the digit line to a third voltage or a fourthvoltage for a write back operation following reading the first logicstate, where at least one of the third voltage or the fourth voltage isdifferent than the first voltage and the second voltage.

In some examples of the method 800 and the apparatus described herein,reading the first logic state includes comparing a voltage generated onthe digit line based on the ferroelectric memory cell with a referencevoltage. In some examples of the method 800 and the apparatus describedherein, writing the second logic state may include operations, features,means, or instructions for selecting the second logic state to be thesame as the first logic state. In some examples of the method 800 andthe apparatus described herein, writing the second logic state mayinclude operations, features, means, or instructions for inverting thefirst logic state to obtain the second logic state.

Some examples of the method 800 and the apparatus described herein mayfurther include operations, features, means, or instructions forcontrolling a first slew rate of the digit line when applying the thirdvoltage. In some examples of the method 800 and the apparatus describedherein, controlling the first slew rate of the digit line when applyingthe third voltage may include operations, features, means, orinstructions for controlling a current sourced to the digit line whenapplying the third voltage. Some examples of the method 800 and theapparatus described herein may further include operations, features,means, or instructions for controlling a second slew rate of the digitline when driving the digit line from the third voltage to the fourthvoltage. Some examples of the method 800 and the apparatus describedherein may further include operations, features, means, or instructionsfor controlling a current removed from the digit line when driving thedigit line from the third voltage to the fourth voltage.

FIG. 9 shows a flowchart illustrating a method or methods 900 thatsupports access line disturbance mitigation in accordance with aspectsof the present disclosure. The operations of method 900 may beimplemented by a memory device or its components as described herein.For example, the operations of method 900 may be performed by a memorydevice as described with reference to FIG. 7. In some examples, a memorydevice may execute a set of instructions to control the functionalelements of the memory device to perform the described functions.Additionally or alternatively, a memory device may perform aspects ofthe described functions using special-purpose hardware.

At 905, the memory device may read a first logic state of aferroelectric memory cell, the reading including coupling a sensecircuit to a digit line associated with the ferroelectric memory celland latching, at the sense circuit, a first voltage or a second voltage.The operations of 905 may be performed according to the methodsdescribed herein. In some examples, aspects of the operations of 905 maybe performed by a read component as described with reference to FIG. 7.

At 910, the memory device may decouple the sense circuit from the digitline based on latching the first voltage or the second voltage. Theoperations of 910 may be performed according to the methods describedherein. In some examples, aspects of the operations of 910 may beperformed by a coupling component as described with reference to FIG. 7.

At 915, the memory device may write a second logic state back to theferroelectric memory cell, the writing including driving the digit lineto a third voltage or a fourth voltage for a write back operationfollowing reading the first logic state, where at least one of the thirdvoltage or the fourth voltage is different than the first voltage andthe second voltage. The operations of 915 may be performed according tothe methods described herein. In some examples, aspects of theoperations of 915 may be performed by a write component as describedwith reference to FIG. 7.

At 920, the memory device may control a first slew rate of the digitline when applying the third voltage. The operations of 920 may beperformed according to the methods described herein. In some examples,aspects of the operations of 920 may be performed by a slew ratecomponent as described with reference to FIG. 7.

FIG. 10 shows a flowchart illustrating a method or methods 1000 thatsupports access line disturbance mitigation in accordance with aspectsof the present disclosure. The operations of method 1000 may beimplemented by a memory device or its components as described herein.For example, the operations of method 1000 may be performed by a memorydevice as described with reference to FIG. 7. In some examples, a memorydevice may execute a set of instructions to control the functionalelements of the memory device to perform the described functions.Additionally or alternatively, a memory device may perform aspects ofthe described functions using special-purpose hardware.

At 1005, the memory device may read a first logic state of aferroelectric memory cell, the reading including coupling a sensecircuit to a digit line associated with the ferroelectric memory celland latching, at the sense circuit, a first voltage or a second voltage.The operations of 1005 may be performed according to the methodsdescribed herein. In some examples, aspects of the operations of 1005may be performed by a read component as described with reference to FIG.7.

At 1010, the memory device may decouple the sense circuit from the digitline based on latching the first voltage or the second voltage. Theoperations of 1010 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1010 may beperformed by a coupling component as described with reference to FIG. 7.

At 1015, the memory device may couple the sense circuit with a writecircuit based on latching the first voltage or the second voltage. Theoperations of 1015 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1015 may beperformed by a coupling component as described with reference to FIG. 7.

At 1020, the memory device may write a second logic state to theferroelectric memory cell, the writing including controlling a firstslew rate of the digit line for driving the digit line to a thirdvoltage that is higher than the first voltage or the second voltage. Theoperations of 1020 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1020 may beperformed by a write component as described with reference to FIG. 7.

In some examples, an apparatus as described herein may perform a methodor methods, such as the method 1000. The apparatus may include features,means, or instructions (e.g., a non-transitory computer-readable mediumstoring instructions executable by a processor) for reading a firstlogic state of a ferroelectric memory cell, the reading includingcoupling a sense circuit to a digit line associated with theferroelectric memory cell and latching, at the sense circuit, a firstvoltage or a second voltage, decoupling the sense circuit from the digitline based on latching the first voltage or the second voltage, couplingthe sense circuit with a write circuit based on latching the firstvoltage or the second voltage, and writing a second logic state to theferroelectric memory cell, the writing including controlling a firstslew rate of the digit line for driving the digit line to a thirdvoltage that is higher than the first voltage or the second voltage.

Some examples of the method 1000 and the apparatus described herein mayfurther include operations, features, means, or instructions for writingthe second logic state to the ferroelectric memory cell includescontrolling, after driving the digit line to the third voltage, a secondslew rate of the digit line for driving the digit line from the thirdvoltage to a fourth voltage. In some examples of the method 1000 and theapparatus described herein, the first logic state may be the same as thesecond logic state. In some examples of the method 1000 and theapparatus described herein, the first logic state may be different thanthe second logic state. Some examples of the method 1000 and theapparatus described herein may further include operations, features,means, or instructions for selectively coupling the digit lineassociated with the ferroelectric memory cell with the sense circuit forreading the first logic state and writing the second logic state.

FIG. 11 shows a flowchart illustrating a method or methods 1100 thatsupports access line disturbance mitigation in accordance with aspectsof the present disclosure. The operations of method 1100 may beimplemented by a memory device or its components as described herein.For example, the operations of method 1100 may be performed by a memorydevice as described with reference to FIG. 7. In some examples, a memorydevice may execute a set of instructions to control the functionalelements of the memory device to perform the described functions.Additionally or alternatively, a memory device may perform aspects ofthe described functions using special-purpose hardware.

At 1105, the memory device may read a first logic state of aferroelectric memory cell, the reading including coupling a sensecircuit to a digit line associated with the ferroelectric memory celland latching, at the sense circuit, a first voltage or a second voltage.The operations of 1105 may be performed according to the methodsdescribed herein. In some examples, aspects of the operations of 1105may be performed by a read component as described with reference to FIG.7.

At 1110, the memory device may decouple the sense circuit from the digitline based on latching the first voltage or the second voltage. Theoperations of 1110 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1110 may beperformed by a coupling component as described with reference to FIG. 7.

At 1115, the memory device may couple the sense circuit with a writecircuit based on latching the first voltage or the second voltage. Theoperations of 1115 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1115 may beperformed by a coupling component as described with reference to FIG. 7.

At 1120, the memory device may write a second logic state to theferroelectric memory cell, the writing including controlling a firstslew rate of the digit line for driving the digit line to a thirdvoltage that is higher than the first voltage or the second voltage. Theoperations of 1120 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1120 may beperformed by a write component as described with reference to FIG. 7.

At 1125, the memory device may control, after driving the digit line tothe third voltage, a second slew rate of the digit line for driving thedigit line from the third voltage to a fourth voltage. The operations of1125 may be performed according to the methods described herein. In someexamples, aspects of the operations of 1125 may be performed by a slewrate component as described with reference to FIG. 7.

It should be noted that the methods described above describe possibleimplementations, and that the operations and the steps may be rearrangedor otherwise modified and that other implementations are possible.Furthermore, portions from two or more of the methods may be combined.

An apparatus is described. The apparatus may include a ferroelectricmemory cell coupled with a row line and a digit line, a sense circuitcoupled with the digit line and configured to determine a first logicstate of the ferroelectric memory cell by latching a first voltage or asecond voltage for a read operation of the ferroelectric memory cell,and a write circuit coupled with the digit line and the sense circuit,the write circuit configured to write a second logic state to theferroelectric memory cell based on the first voltage or the secondvoltage latched by the sense circuit and write the second logic state byapplying a third voltage or a fourth voltage to the digit line for awrite back operation following the read operation, where at least one ofthe third voltage or the fourth voltage is different than the firstvoltage and the second voltage.

In some examples, the sense circuit further includes a sense amplifierselectively couplable with the digit line and configured to sense acharge state stored on the ferroelectric memory cell. In some examples,the write circuit may be coupled with the sense circuit via a firstswitchable path setting the second logic state to a same state as thefirst logic state and a second switchable path setting the second logicstate to be inverted from the first logic state. In some examples, thethird voltage may be a higher voltage than the first voltage or thesecond voltage, where the write circuit includes a switch that couplesan input node of the write circuit to the third voltage and decouplesthe input node from the third voltage before the coupling of the sensecircuit to the write circuit via the first switchable path or the secondswitchable path.

In some examples, the write circuit further includes a feedbacktransistor that couples an output node of the write circuit to the inputnode after the write circuit applies the third voltage or the fourthvoltage to the digit line. In some examples, the write circuit includesa level shifter circuit configured to apply the third voltage or thefourth voltage to the digit line for a write back operation. In someexamples, the level shifter circuit may be configured to control a slewrate of applying the third voltage or the fourth voltage to the digitline for a write back operation. In some examples, the level shiftercircuit includes a first current driver configured to apply a firstcurrent for controlling the slew rate of applying the third voltage anda second current driver configured to apply a second current forcontrolling the slew rate of applying the fourth voltage.

In some examples, the third voltage may be a higher voltage than thefirst voltage or the second voltage, where, for the second logic statebeing associated with applying the third voltage for the writeoperation, the second current driver may be configured to control theslew rate of the digit line from the third voltage to the fourth voltageat an end of the write back operation. In some examples, the digit linemay be a first digit line and the ferroelectric memory cell may be afirst ferroelectric memory cell that may be accessible via a word lineand the first digit line, and where the memory device includes a secondferroelectric memory cell accessible via the word line and a seconddigit line, and where the second digit line may be decoupled from thesense circuit and the write circuit for the read operation and the writeback operation via a switch.

In some examples, the sense circuit may be coupled with a first supplyvoltage and the write circuit may be coupled with a second supplyvoltage that may be higher than the first supply voltage. In someexamples, the sense circuit includes a latch for latching the firstvoltage or the second voltage for the read operation, the latchincluding a first set of transistors having a first gate oxidethickness, where the write circuit includes a driver for applying thethird voltage or the fourth voltage to the digit line for the write backoperation, the driver including a second set of transistors having asecond gate oxide thickness.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof. Some drawings may illustrate signals as a single signal;however, it will be understood by a person of ordinary skill in the artthat the signal may represent a bus of signals, where the bus may have avariety of bit widths.

As used herein, the term “virtual ground” refers to a node of anelectrical circuit that is held at a voltage of approximately zero volts(0V) but that is not directly coupled with ground. Accordingly, thevoltage of a virtual ground may temporarily fluctuate and return toapproximately 0V at steady state. A virtual ground may be implementedusing various electronic circuit elements, such as a voltage dividerconsisting of operational amplifiers and resistors. Otherimplementations are also possible. “Virtual grounding” or “virtuallygrounded” means connected to approximately 0V.

The terms “electronic communication,” “conductive contact,” “connected,”and “coupled” may refer to a relationship between components thatsupports the flow of signals between the components. Components areconsidered in electronic communication with (or in conductive contactwith or connected with or coupled with) one another if there is anyconductive path between the components that can, at any time, supportthe flow of signals between the components. At any given time, theconductive path between components that are in electronic communicationwith each other (or in conductive contact with or connected with orcoupled with) may be an open circuit or a closed circuit based on theoperation of the device that includes the connected components. Theconductive path between connected components may be a direct conductivepath between the components or the conductive path between connectedcomponents may be an indirect conductive path that may includeintermediate components, such as switches, transistors, or othercomponents. In some examples, the flow of signals between the connectedcomponents may be interrupted for a time, for example, using one or moreintermediate components such as switches or transistors.

The term “coupling” refers to condition of moving from an open-circuitrelationship between components in which signals are not presentlycapable of being communicated between the components over a conductivepath to a closed-circuit relationship between components in whichsignals can be communicated between components over the conductive path.When a component, such as a controller, couples other componentstogether, the component initiates a change that allows signals to flowbetween the other components over a conductive path that previously didnot permit signals to flow.

The term “isolated” refers to a relationship between components in whichsignals are not presently capable of flowing between the components.Components are isolated from each other if there is an open circuitbetween them. For example, two components separated by a switch that ispositioned between the components are isolated from each other when theswitch is open. When a controller isolates two components from oneanother, the controller affects a change that prevents signals fromflowing between the components using a conductive path that previouslypermitted signals to flow.

The term “layer” used herein refers to a stratum or sheet of ageometrical structure. Each layer may have three dimensions (e.g.,height, width, and depth) and may cover at least a portion of a surface.For example, a layer may be a three-dimensional structure where twodimensions are greater than a third, e.g., a thin-film. Layers mayinclude different elements, components, and/or materials. In someexamples, one layer may be composed of two or more sublayers. In some ofthe appended figures, two dimensions of a three-dimensional layer aredepicted for purposes of illustration.

As used herein, the term “electrode” may refer to an electricalconductor, and in some examples, may be employed as an electricalcontact to a memory cell or other component of a memory array. Anelectrode may include a trace, wire, conductive line, conductive layer,or the like that provides a conductive path between elements orcomponents of memory array.

The devices discussed herein, including a memory array, may be formed ona semiconductor substrate, such as silicon, germanium, silicon-germaniumalloy, gallium arsenide, gallium nitride, etc. In some examples, thesubstrate is a semiconductor wafer. In other examples, the substrate maybe a silicon-on-insulator (SOI) substrate, such as silicon-on-glass(SOG) or silicon-on-sapphire (SOP), or epitaxial layers of semiconductormaterials on another substrate. The conductivity of the substrate, orsub-regions of the substrate, may be controlled through doping usingvarious chemical species including, but not limited to, phosphorous,boron, or arsenic. Doping may be performed during the initial formationor growth of the substrate, by ion-implantation, or by any other dopingmeans.

A switching component or a transistor discussed herein may represent afield-effect transistor (FET) and comprise a three terminal deviceincluding a source, drain, and gate. The terminals may be connected toother electronic elements through conductive materials, e.g., metals.The source and drain may be conductive and may comprise a heavily-doped,e.g., degenerate, semiconductor region. The source and drain may beseparated by a lightly-doped semiconductor region or channel. If thechannel is n-type (i.e., majority carriers are electrons), then the FETmay be referred to as a n-type FET. If the channel is p-type (i.e.,majority carriers are holes), then the FET may be referred to as ap-type FET. The channel may be capped by an insulating gate oxide. Thechannel conductivity may be controlled by applying a voltage to thegate. For example, applying a positive voltage or negative voltage to ann-type FET or a p-type FET, respectively, may result in the channelbecoming conductive. A transistor may be “on” or “activated” when avoltage greater than or equal to the transistor's threshold voltage isapplied to the transistor gate. The transistor may be “off” or“deactivated” when a voltage less than the transistor's thresholdvoltage is applied to the transistor gate.

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details toproviding an understanding of the described techniques. Thesetechniques, however, may be practiced without these specific details. Insome instances, well-known structures and devices are shown in blockdiagram form to avoid obscuring the concepts of the described examples.

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an ASIC, an FPGA or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. A general-purpose processor may be a microprocessor,but in the alternative, the processor may be any processor, controller,microcontroller, or state machine. A processor may also be implementedas a combination of computing devices (e.g., a combination of a DSP anda microprocessor, multiple microprocessors, one or more microprocessorsin conjunction with a DSP core, or any other such configuration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations. Also, as used herein, including in the claims, “or” as usedin a list of items (for example, a list of items prefaced by a phrasesuch as “at least one of” or “one or more of”) indicates an inclusivelist such that, for example, a list of at least one of A, B, or C meansA or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, asused herein, the phrase “based on” shall not be construed as a referenceto a closed set of conditions. For example, an exemplary step that isdescribed as “based on condition A” may be based on both a condition Aand a condition B without departing from the scope of the presentdisclosure. In other words, as used herein, the phrase “based on” shallbe construed in the same manner as the phrase “based at least in parton.”

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media cancomprise RAM, ROM, electrically erasable programmable read-only memory(EEPROM), compact disk (CD) ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any othernon-transitory medium that can be used to carry or store desired programcode means in the form of instructions or data structures and that canbe accessed by a general-purpose or special-purpose computer, or ageneral-purpose or special-purpose processor. Also, any connection isproperly termed a computer-readable medium. For example, if the softwareis transmitted from a website, server, or other remote source using acoaxial cable, fiber optic cable, twisted pair, digital subscriber line(DSL), or wireless technologies such as infrared, radio, and microwave,then the coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave are included in the definition of medium. Disk and disc,as used herein, include CD, laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be apparent to those skilled in the art, and the generic principlesdefined herein may be applied to other variations without departing fromthe scope of the disclosure. Thus, the disclosure is not limited to theexamples and designs described herein but is to be accorded the broadestscope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. An apparatus, comprising: a ferroelectric memorycell couplable with a digit line; a sense circuit couplable with thedigit line and configured to determine a first logic state of theferroelectric memory cell by latching a first voltage for a readoperation of the ferroelectric memory cell; and a write circuitcouplable with the digit line and the sense circuit, the write circuitconfigured to write a second logic state to the ferroelectric memorycell based at least in part on the first voltage latched by the sensecircuit and by applying a second voltage to the digit line for a writeback operation following the read operation, wherein the write circuitcontrols a first slew rate of applying the second voltage to the digitline for the write back operation.
 2. The apparatus of claim 1, whereinthe write circuit is further configured to control a second slew ratewhen driving the digit line from the second voltage to a third voltage.3. The apparatus of claim 1, wherein the write circuit is furtherconfigured to control the first slew rate by controlling a currentsourced to the digit line when applying the second voltage.
 4. Theapparatus of claim 1, wherein the sense circuit further comprises asense amplifier selectively coupled with the digit line and configuredto compare a reference voltage with a voltage generated on the digitline based at least in part on the ferroelectric memory cell.
 5. Theapparatus of claim 4, wherein the write circuit is coupled with thesense circuit via a first switchable path setting the second logic stateto a same state as the first logic state and a second switchable pathsetting the second logic state to be inverted from the first logicstate.
 6. The apparatus of claim 5, wherein the second voltage is ahigher voltage than the first voltage, and wherein the write circuitcomprises a switch that couples an input node of the write circuit tothe second voltage and decouples the input node from the second voltagebefore the coupling of the sense circuit to the write circuit via thefirst switchable path or the second switchable path.
 7. The apparatus ofclaim 6, wherein the write circuit further comprises a feedbacktransistor that couples an output node of the write circuit to the inputnode after the write circuit applying the second voltage to the digitline.
 8. The apparatus of claim 1, wherein the write circuit comprises alevel shifter circuit configured to apply the second voltage to thedigit line for a write back operation, the level shifter circuitconfigured to control the first slew rate of applying the second voltageto the digit line for the write back operation.
 9. The apparatus ofclaim 8, wherein the level shifter circuit comprises a first currentdriver configured to apply a first current for controlling the firstslew rate of applying the second voltage.
 10. The apparatus of claim 9,wherein the second voltage is a higher voltage than the first voltage,and wherein the level shifter circuit further comprises a second currentdriver that is configured to control a second slew rate of the digitline from the second voltage to a third voltage at an end of the writeback operation.
 11. The apparatus of claim 1, wherein the digit line isa first digit line and the ferroelectric memory cell is a firstferroelectric memory cell that is accessible via a word line and thefirst digit line, and wherein the apparatus comprises a secondferroelectric memory cell accessible via the word line and a seconddigit line, and wherein the second digit line is decoupled from thesense circuit and the write circuit for the read operation and the writeback operation via a switch.
 12. The apparatus of claim 1, wherein thesense circuit is coupled with a first supply voltage and the writecircuit is coupled with a second supply voltage that is higher than thefirst supply voltage.
 13. The apparatus of claim 1, wherein the sensecircuit comprises a latch for latching the first voltage for the readoperation, the latch comprising a first plurality of transistors havinga first gate oxide thickness, and wherein the write circuit comprises adriver for applying the second voltage to the digit line for the writeback operation, the driver comprising a second plurality of transistorshaving a second gate oxide thickness.
 14. A method, comprising: readinga first logic state of a ferroelectric memory cell, the readingcomprising coupling a sense circuit to a digit line associated with theferroelectric memory cell and latching, at the sense circuit, a firstvoltage; decoupling the sense circuit from the digit line based at leastin part on latching the first voltage; and writing a second logic stateto the ferroelectric memory cell based at least in part on decouplingthe sense circuit, the writing comprising controlling a first slew ratefor driving the digit line to a second voltage.
 15. The method of claim14, wherein the writing further comprises: controlling a second slewrate when driving the digit line from the second voltage to a thirdvoltage.
 16. The method of claim 14, wherein the writing furthercomprises: controlling the first slew rate by controlling a currentsourced to the digit line when applying the second voltage.
 17. Themethod of claim 14, further comprising: coupling the sense circuit witha write circuit based at least in part on latching the first voltage.18. The method of claim 14, wherein the second voltage is higher thanthe first voltage.
 19. An apparatus, comprising: a ferroelectric memorycell couplable with a digit line; a sense circuit couplable with thedigit line; a write circuit couplable with the digit line and the sensecircuit; and a controller operable to cause the apparatus to: read afirst logic state of the ferroelectric memory cell, the readingcomprising coupling the sense circuit to the digit line and latching, atthe sense circuit, a first voltage; decouple the sense circuit from thedigit line based at least in part on latching the first voltage; andwrite a second logic state to the ferroelectric memory cell via thewrite circuit, the writing comprising controlling a first slew rate fordriving the digit line to a second voltage.
 20. The apparatus of claim19, wherein the controller is further operable to cause the apparatusto: control a second slew rate when driving the digit line from thesecond voltage to a third voltage, wherein writing the second logicstate is based at least in part on controlling the second slew rate.